Each week, Sports on Earth is counting down the best returning college football players at every position entering the 2017 season. These rankings are based on a combination of talent, proven production and potential at the college level. They are not NFL Draft rankings. Check out our top 30 wide receivers/top 15 tight ends and top 35 linebackers.

The NFL Draft's running back class of 2017 was loaded, including first-round picks Leonard Fournette and Christian McCaffrey, but with juniors like Saquon Barkley, Derrius Guice and Bo Scarbrough and returning seniors like Nick Chubb, Royce Freeman and Justin Jackson, there is still a wealth of running back talent remaining at the college level entering this season. Our rankings break down the top 40 returning (potential star freshmen like Florida State's Cam Akers are thus not eligible for this list) players at the position.

40. Tony Brooks-James, Oregon. The Ducks' backfield is loaded. Royce Freeman is the bell-cow back, and he's supported by a talented group that includes Kani Benoit, Taj Griffin and Brooks-James. The 180-pound Brooks-James is a familiar type of all-purpose back for Oregon, and it's likely that the new staff will find creative ways to get him the ball after he averaged 7.6 yards per carry as a sophomore, rushing 101 times for 771 yards and nine TDs.

39. Kalen Ballage, Arizona State. Ballage's production unfortunately disproportionately came against Texas Tech's horrid run defense, when he had eight touchdowns in one game and, with 137 rushing yards, accounted for a quarter of his season rushing output on one night. Still, he's a powerful 227-pound back who also caught 44 passes for 469 yards, and he forms a strong running back duo with Demario Richard.

38. James Gilbert, Ball State. A huge midseason stretch spurred Gilbert to a breakout sophomore season in which he ran for 1,332 yards and 12 TDs. He had 264 yards against Buffalo in the middle of a five-game streak of 100-yard games. The 5-foot-8, 191-pound Gilbert will now be one of the biggest stars returning to the MAC, leading a potent Cardinals ground game that also includes the mobile Riley Neal at quarterback.

37. James Butler, Iowa. When we originally wrote this, Butler was ready for a senior season in Reno in which he'd be the best player on the Nevada roster. The Wolf Pack switched to an Air Raid offense under new coach Jay Norvell, though, and Butler announced on July 4 that he'll be a graduate transfer to Iowa. It's a big pickup for the Hawkeyes, who had two 1,000-yard backs last year and, despite losing LeShun Daniels, now will still have two 1,000-yard backs in Butler (1,336 yards at Nevada) and Akrum Wadley (1,081 yards, 6.4 yards per carry). Wadley will be the star, but Butler is an excellent addition with 3,316 career rushing yards.

36. Josh Adams, Notre Dame. In a season filled with frustration for Notre Dame, Adams at least had some positive moments in his sophomore season, including a career-high 180 yards in the season-ending loss to USC. Adams averages 6.5 yards per carry in his two seasons, and he's the leader of a stellar group of Fighting Irish tailbacks who will make the transition a bit easier for new QB Brandon Wimbush.

35. Ryan Nall, Oregon State. Nall is built like a linebacker at 6-foot-2, 239 pounds, and he started his career as a tight end/H-back. That made him quite the revelation for the Beavers at tailback in his sophomore season, as he ended up rushing 147 times for 951 yards and 13 TDs, averaging 6.5 yards per carry. He would have easily been a thousand-yard rusher had it not been for injuries. Nall had 221 yards against Cal and 155 against Oregon, and he's also an adept receiver, hauling in 22 catches. Given the uncertainty in Oregon State's passing game, the physicality and productivity of Nall was a much-needed development for a team trying to climb out of the Pac-12 basement.

34. Ty Johnson, Maryland. Johnson emerged as a big-play machine under new coordinator Walt Bell last year, rushing for 1,004 yards on only 110 carries, an average of 9.1 per rush. He was 21st in the Big Ten in carries and yet led the conference with 10 runs of 30-plus yards -- three more than any other player. The Terps' passing game has a long way to go, but one thing became clear in 2016: get the ball to Johnson in space.

33. Bryce Love, Stanford. Love has a task that's nearly impossible. Nobody can replace Christian McCaffrey, a Heisman Trophy finalist who set the single-season all-purpose yardage record and rushed for nearly 4,000 yards in his Stanford career. But there is no question that Love is a talented replacement, and he's ready for a breakout season. Love already got a chance to replace McCaffrey in the Sun Bowl, and he rushed for 119 yards and had a 49-yard receiving TD in the Cardinal's win over North Carolina. In total last year as a sophomore, Love rushed for 783 yards and average seven yards per carry. He's not McCaffrey, but he's an explosive talent ready to thrive and make a name for himself in an expanded role.

32. Larry Rose III, New Mexico State. Two years ago, Rose was one of the nation's most productive rushers, racking up 1,651 yards with an average of 6.9 yards per carry. Unfortunately, injuries slowed him as a junior, as he missed the first three games and ultimately ran for 865 yards in nine games. Now, in the Aggies' Sun Belt farewell season, the hope is that Rose can recapture previous form, when he was named 2015 Sun Belt offensive player of the year. Given the way he ended 2016 -- including 170 yards in the finale against South Alabama -- he very well might do that.

31. Damarea Crockett, Missouri. Missouri fell from 5-7 to 4-8 last season, and yet the offense improved from 125th to 31st in yards per play in Josh Heupel's first year as coordinator. QB Drew Lock made strides, and the Tigers also got a breakout performance on the ground from Crockett, who, as a 220-pound freshman, rushed for 1,062 yards and 10 TDs on only 153 carries -- an average of 6.9 per attempt. While the Tigers got blown out in the game, Crockett's final performance of 2016 featured 225 yards against Tennessee, before a season-ending one-game suspension.

30. Ray Lawry, Old Dominion. In only their third season of FBS play, the Monarchs won 10 games, with a six-game winning streak to end the season led by the fabulous running of Lawry. Lawry had at least 117 yards in five of those games, including 209 against Marshall and 194 against FIU. The 5-foot-10, 204-pound senior averages 6.3 yards per carry with 3,338 career rushing yards thanks to his burst and shiftiness in the open field.

29. Terence Williams, Baylor. With Shock Linwood falling out of favor and Johnny Jefferson out for the 2016 season, Williams emerged as the Bears' top rusher as a sophomore. At 220 pounds, Williams ran 185 times for 1,048 yards and 11 TDs, ensuring that the Bears would have at least one 1,000-yard rusher for the seventh straight season. Williams is a powerful, hard-running back for a new-look offense under coach Matt Rhule, and he teams with the smaller JaMycal Hasty to former a potent one-two punch.

28. L.J. Scott, Michigan State. Regardless of what happens the rest of his Michigan State career, it will be hard for Scott to surpass his big moment as a freshman, when he fought for every last inch to score the winning touchdown against Iowa in the 2015 Big Ten title game. The 231-pound junior emerged as the clear-cut lead runner last season after a committee approach in2015, as his 184 carries (for 994 yards and six TDs) were more than twice as many attempts as anyone else on the Spartans. Scott played well in the second half of the season, and if the line takes a step forward, he should achieve his first thousand-year season as the Spartans try to bounce back.

27. D'Angelo Brewer, Tulsa. The Golden Hurricane, led by former Baylor offensive coordinator Philip Montgomery, averaged over 50 rush attempts per game last season, resulting in two running backs who had over 1,400 yards. James Flanders is gone, but Brewer is back for his senior year after rushing for 1,435 yards and seven TDs. Tulsa will likely find another option to prevent the 185-pound Brewer from being overworked, but with most of the line back and a new-look passing game, the offense is sure to lean on him heavily.

26. Sony Michel, Georgia. Back in 2014, Georgia signed two five-star running backs in Michel and Nick Chubb. They have rushed for a combined 5,810 yards over three seasons. Somehow, both are back for their senior seasons, something the Bulldogs never expected. Chubb, who returned from a bad knee injury last year, is the clear lead runner, but Michel still had 152 carries for 840 yards an four TDs last year, and his production could grow a bit if the Georgia offensive line improves.

25. Rodney Smith, Minnesota. Smith and Shannon Brooks have shared the load in the Golden Gophers' backfield their first two seasons, but Smith has gotten a bit more work, including 240 carries for 1,158 yards and 16 TDs in 2016. He had six 100-yard games and has emerged as a reliable, underrated back who will be the offense's most important player with a veteran line but a new-look passing game.

24. Benjamin Snell, Kentucky. After a tough start to the season, Kentucky ended up winning six games to get to a bowl for the first time since 2010. The two players most responsible were Snell and Boom Williams, who fueled a rushing offense that averaged 234 yards per game. Williams, who was a 196-pound junior, ran for 1,170 yards and seven TDs, averaging 6.8 yards per carry. Snell, who was a 220-pound freshman, ran for 1,091 yards and 13 TDs, averaging 5.9 yards per carry. With Williams turning pro, it's Snell's show at tailback now.

23. Jarvion Franklin, Western Michigan. Franklin shined as a freshman with 1,551 yards, saw his production cut in half as a sophomore and returned to form as a junior with 1,353 yards and 12 TDs. He shares carries with Jamauri Bogan, who has over 900 yards each of the past two seasons, but the 6-foot, 225-pound senior Franklin has 3,639 yards and 41 TDs in his career. Western Michigan can be expected to lean on the one-two punch of Franklin and the smaller (192 pounds) Bogan with QB Zach Terrell and WR Corey Davis both gone.

22. Phillip Lindsay, Colorado. Lindsay's midseason tear helped spur the Buffaloes to their improbable division title. He finished with 1,252 yards and 16 TDs, largely on the back of a five-game span in which he had 219 against Arizona State, 131 against Stanford, 119 against Arizona and 144 against Washington State. The 5-foot-8, 180-pound Lindsay became the Buffaloes' first thousand-yard back since 2010, and he also had 53 catches for 493 yards, proving to be a valuable, versatile weapon who's a natural pass catcher and played a big role in the improved efficiency of the Colorado offense.

21. Jalin Moore, Appalachian State. Moore showed signs of stardom late in his freshman season in 2015 -- including a 244-yard game at Idaho -- and he built on that to become the Mountaineers' leading rusher with veteran standout Marcus Cox missing four games with an injury. While Cox was a big part of the offense when healthy, Moore's production didn't let up. He ran 237 times for 1,402 yards and 10 TDs, with 257 yards against Akron and seven other 100-yard performances. He also had 10 runs of at least 30 yards. Moore earned Sun Belt offensive player of the year honors, and now he becomes the clear-cut lead back with Cox moving on.

20. Trayveon Williams, Texas A&M. Oklahoma transfer Keith Ford was presumably in line to be the Aggies' new lead runner, alongside Oklahoma transfer QB Trevor Knight. Instead, the freshman Williams emerged as Texas A&M's best tailback option. He averaged 6.8 yards per carry, rushing for 1,057 yards and eight TDs, although his production matched another Texas A&M second-half collapse by dwindling later in the season. With uncertainty at quarterback, the Aggies may lean heavily on Williams and Ford to carry the offense, particularly early in the season.

19. Justin Crawford, West Virginia. Dana Holgorsen may come from a Mike Leach/Air Raid background, but he has embraced the running game at West Virginia. It helps that, after Wendell Smallwood and his 1,519 yards in 2015 left, Crawford, a juco transfer, emerged to take over the backfield with Rushel Shell in a supporting role. The 6-foot, 202-pound Crawford had a few impressive games in the first half of the season, then emerged with two mammoth second-half performances: 331 yards in a loss to Oklahoma on a frigid night and 209 yards in a win over Baylor.

18. Rashaad Penny, San Diego State. Yes, San Diego State played 14 games last year with its familiar run-heavy offense, but it nevertheless feels impossible that the Aztecs could have a thousand-yard back in addition to Donnel Pumphrey, the record-setting runner who had 349 carries for 2,133 yards as a senior. And yet, Penny managed to make the most of his opportunities, averaging 7.5 yards per carry behind Pumphrey with 136 attempts for 1,018 yards and 11 TDs. He also caught 15 passes and returned two kickoffs for touchdowns. At 220 pounds, Penny is much bigger than Pumphrey, and after cracking 100 yards five times as a reserve, he's set for a huge portion of carries with Pumphrey in the NFL.

17. Kyle Hicks, TCU. Hicks stepped up into the starting lineup and performed well as a junior, albeit as part of an inconsistent Horned Frogs offense. He ran for 1,042 yards in 12 games with 12 touchdowns, headlined by his ridiculous 192-yard, five-TD performance in a win over Baylor. Hicks' value was bolstered by his production in the passing game, as he was a consistent weapon who caught 47 passes for 412 yards and two TDs, placing him in the team lead in receptions.

16. Ito Smith, Southern Miss. Smith was a 1,000-yard back despite sharing the backfield with Jalen Richard in 2015. With Richard gone, Smith had 1,918 yards from scrimmage, rushing for 1,459 yards and 17 TDs and catching 43 passes for 459 yards and two TDs. The 5-foot-9, 195-pound senior is one of the nation's most dynamic and versatile tailbacks, one who runs with physicality despite his size. He showed last year that he can handle a big workload as a runner, and it didn't diminish his contributions to the passing game, either.

15. Damien Harris, Alabama. Remember him? Harris was overshadowed by Bo Scarbrough late in the season, but he was also a five-star recruit, too, and he's the one who became a thousand-yard back. With Heisman winner Derrick Henry off to the NFL, Harris had 146 carries for 1,037 yards and two TDs, averaging 7.1 yards per carry. His workload is going to have a ceiling because of the presence of Scarbrough and other talented tailbacks in an incredibly deep rotation, plus the heavy running workload of QB Jalen Hurts. But Harris is a talented, dynamic runner, even if he's not the physically overwhelming player that Scarbrough is.

14. Ralph Webb, Vanderbilt. Webb hasn't had explosive offenses around him, but he's been a consistent weapon, grinding out tough yards as a three-year starter. His junior season was his best yet, as he carried 250 times for 1,283 yards and 13 TDs, including a strong finish to the season. The second-team All-SEC pick is already Vanderbilt's all-time leading rusher with 3,143 career yards.

13. Mike Weber, Ohio State. Weber had massive shoes to fill as a redshirt freshman in replacing Ezekiel Elliott in the lineup. Ohio State avoided putting everything on his shoulders, as QB J.T. Barrett actually led the team in rush attempts and Curtis Samuel played a big role, too. But Weber had a stellar debut season, rushing 182 times for 1,096 yards and nine TDs, giving him an average of six yards per carry. The Buckeyes offense should improve with Kevin Wilson stepping in as offensive coordinator, and the quick and powerful Weber has a chance to significantly improve upon a stellar 2016 with a heavier workload after he often got between 10-15 carries per game.

12. Mark Walton, Miami. The Hurricanes returned a thousand-yard back in Joseph Yearby last year, but Walton, a star recruit in 2015, stepped ahead of Yearby as a sophomore and looked like a burgeoning star. The 5-foot-9, 205-pound Walton ran 209 times for 1,117 yards and 14 TDs, and he also caught 27 passes for 240 yards and a TD. Yearby turned pro and Gus Edwards transferred to Rutgers, leaving Walton as the only running back with any experience in the Miami backfield. He's the best returning tailback in the ACC, in fact, and is poised to become the focal point of the Canes' offense.

11. Akrum Wadley, Iowa. The underrated Wadley received 45 fewer carries than teammate LeShun Daniels last season, but he rushed for 23 more yards. Wadley had 168 carries for 1,068 yards and 10 TDs (6.4 per carry), and he caught 36 passes for 315 yards and three TDs. While he's not big at 5-foot-11, 185 pounds, he's a talented, shifty, multi-dimensional weapon, and despite the loss of Daniels, he still won't have to do everything now that the Hawkeyes have brought in James Butler from Nevada as a graduate transfer. 

10. Myles Gaskin, Washington. After a somewhat slow start to his sophomore season, Gaskin took off like the rest of the Huskies in Pac-12 play, ultimately racking up 1,373 yards and 10 TDs. Lavon Coleman gets a significant amount of work as a rotational back, but despite being 5-foot-9, 192 pounds, Gaskin is the workhorse, with 464 carries in his first two seasons. Gaskin is a smooth runner with quick feet that allow him to weave through traffic and keep this offense on schedule.

9. Justice Hill, Oklahoma State. After a couple years of dismal rushing offenses, the Cowboys found new life thanks to Hill, who emerged as a potent weapon in his freshman season. Hill is 5-foot-10, 171 pounds, and he fits well into the Cowboys' spread attack that has a dangerous passing game. With defenses needed to spend so much energy trying to contain Oklahoma State's big-play passing attack, Hill found room to run and ended up with 1,142 yards -- the most by any of the nation's freshmen -- and six TDs, proving to be a steady and reliable option to spark the ground attack with his speed but also a tough, relentless running style.

8. Justin Jackson, Northwestern. Underappreciated in an offense that has often struggled, Jackson was even overshadowed last year by the emergence of star receiver Austin Carr. But even with Carr -- who's now gone -- the Wildcats ranked only 81st nationally in passer rating. Jackson carries the load here, a 5-foot-11, 193-pound senior who has rushed for 4,129 yards and 30 TDs in three years as a starter. The diminutive workhorse did benefit from the expanded passing game last year, as he averaged a career-best 5.1 yards per carry to pile up 1,524 yards, in addition to catching 35 passes. Jackson is tough, agile and versatile.

7. Royce Freeman, Oregon. Freeman's college career couldn't have started much better. He ran for 1,365 yards and 18 TDs as a freshman alongside Marcus Mariota, then he piled up 1,838 yards and 17 yards as a sophomore. He was looking like a sure bet to turn pro after his junior season. Instead, as the Ducks collapsed, Freeman had a frustrating year in which he rushed for 945 yards and nine TDs in nine games, dealing with a knee injury. Freeman decided to return for his senior season under new coach Willie Taggart, and the powerful but nimble 229-pound senior will be the leader of a deep and talented Ducks backfield.

6. Nick Chubb, Georgia. Week 1 last season, it appeared that Chubb had made an absurdly fast recovery back to his old self after a devastating knee injury cut his sophomore season short in 2015. Chubb, who averaged over seven yards per carry his first two seasons, returned to the lineup to pile up 222 yards and two TDs vs. North Carolina. However, due in part to a mediocre offense around him, Chubb wasn't quite his old self the rest of the way, ultimately finishing with 1,130 yards, eight TDs and an average of five yards per carry. Somewhat surprisingly, he returned for his senior season, hoping to recapture the pre-injury magic, when he was every bit as good as Leonard Fournette and Dalvin Cook.

5. Ronald Jones II, USC. Jones shared the backfield with Justin Davis the past two years, but he still led the Trojans in rushing despite splitting carries, with 987 yards as a freshman and 1,082 yards and 12 TDs last season thanks to a big second half of the season. All the attention at USC is now focused on star quarterback Sam Darnold, but Jones could have his own breakthrough to stardom, at least assuming the USC offensive line comes together. Jones averages 6.3 yards per carry in his career, and while he's not particularly powerful at 195 pounds, he runs with burst and elusiveness that allow him to make defenders miss and squeeze through small holes.

4. Kamryn Pettway, Auburn. At the start of last season, the Auburn running back situation was on the verge of disaster. Peyton Barber had left early for the NFL, Roc Thomas chose to transfer and Jovon Robinson was dismissed from the team. Fortunately, reinforcements were waiting: Kerryon Johnson rushed for a team-high 11 touchdowns, but the star became Pettway, who, as a 235-pound sophomore, broke out with 209 carries for 1,224 yards and seven TDs in 10 games, with an average of 138.7 yards per game in seven SEC contests. The powerful Pettway has played some fullback, but he has now firmly established himself as a star SEC running back, one who had over 100 yards seven times, including 236 against Ole Miss. When he gets any room, he's a load to bring down, a punishing runner with quickness.

3. Bo Scarbrough, Alabama. The legend is bigger than the actual tangible results, but there's no mistaking Scarbrough's talent. Injuries have often limited the 6-foot-2, 228-pound junior, who finally emerged as a superstar at the end of last season, only to break his leg during the national championship game. Scarbrough rushed for 812 yards and 11 TDs, with 90-plus yards in each of his last four games, including two TDs before leaving the title game. His biggest performance came in the Peach Bowl, when he tormented Washington for 180 yards and two TDs on the ground. A healthy Scarbrough, with his size, power and agility, has Heisman ability. Two things stand in the way of reaching that potential: 1) durability and 2) getting enough carries. The latter is tough, because Alabama will likely try to limit his wear and tear, especially since it can afford to with the absurd depth it has at running back, including 1,000-yard rusher Damien Harris, promising sophomores Joshua Jacobs and B.J. Emmons and all-world true freshman Najee Harris. There's no doubt that a healthy Scarbrough is a game-changer, though.

2. Derrius Guice, LSU. The Tigers are replacing Leonard Fournette, the No. 4 overall pick in the NFL Draft, with the SEC's leading rusher. With Fournette battling an ankle injury most of last season, we got more than a glimpse at the future. Guice barely played against the two best run defenses LSU faced (Wisconsin and Alabama), but he still averaged an impressive 7.6 yards per carry with 15 touchdowns, racking up 252 yards against Arkansas and 285 against Texas A&M, with four other 100-yard games. He's not as big or powerful as Fournette, but he's a smooth, dynamic runner with balance and agility, making him so tough to get a clean hit on and bring down.

1. Saquon Barkley, Penn State. It doesn't matter what his final rushing total in a game is. At some point over the course of three hours on a Saturday, Barkley is going to do something that ends up in a highlight reel. Barkley's offensive line has been a work in progress his first two seasons, but he's nevertheless done breathtaking things with the football in his hands, ever since he announced his arrival by hurdling a Buffalo defender as a freshman. There's the game-clinching run against Temple. The winning OT touchdown vs. Minnesota. The explosive touchdown against Iowa. The hurdle against Maryland. The spin move in the middle of San Diego State traffic. And there is, of course, the impossible 79-yard run against USC in the Rose Bowl that showed off everything that makes NFL types drool about his potential: the vision, the lateral agility, the explosiveness, the ability to make cuts without losing speed. The 223-pound Barkley is the total package at tailback. After rushing for 1,496 yards and 18 TDs and adding 402 receiving yards as a sophomore, his production will only grow now that he has an improved offensive line and now that defenses are forced to account for a dangerous downfield passing attack.

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Contact Matt at matt.brown5082@gmail.com and follow him on Twitter @MattBrownCFB and Facebook.