Defensive line play is often the biggest difference between the nation's most powerful teams and the rest of the pack, as schools like Alabama and Ohio State are able to hoard massive athletes who can both overpower offensive lines and track down ball carriers and quarterbacks from behind.

There are many big names returning both at defensive end and defensive tackle this season, with stars like Joey Bosa, Robert Nkemdiche, Myles Garrett and Derek Barnett not yet eligible for the pros, and others like Shilique Calhoun, Emmanuel Ogbah and Adolphus Washington deciding to return for another year of college ball. The SEC continues to boast the most defensive line talent, but the Big Ten in particular has also amassed plenty of quality players up front.

So, with less than three months until the 2015 season begins, Part IV of the player rankings series continues by counting down the nation's top 20 defensive ends and top 20 defensive tackles. Check back for offensive line rankings next week.

2015 Player RankingsRunning Backs | Linebackers | Receivers | Defensive Line | Offensive Line | Defensive Backs | Quarterbacks

Defensive Ends

20. Drew Ott, Iowa. A two-year starter, Ott has developed into a reliable force off the edge for the Hawkeyes, with high energy, a quick first step and good instincts. He had 12 tackles for loss, 7 ½ sacks, 57 tackles and an interception as a junior, although now he faces a tougher situation without the services of defensive tackles Carl Davis and Louis Trinca-Pasat next to him.

19. Kamalei Correa, Boise State. Correa broke out as a sophomore last year for the Broncos, becoming the team's top pass rusher with 12 sacks, 19 tackles for loss, two forced fumbles and 59 tackles. He had 10 tackles and two sacks in the Fiesta Bowl win over Arizona, and at 6-foot-3, 244 pounds he gives the Broncos a solid athlete to use off the edge as a hybrid end/linebacker edge rusher.

18. Jonathan Allen, Alabama; and 17. Jarran Reed, Alabama. Alabama's defensive linemen can be hard to classify, and they also don't necessarily put up huge numbers. Reed, a juco transfer last year, slid into a 3-4 defensive end spot at 6-foot-4, 313 pounds, which essentially makes him a tackle. He had 6 ½ tackles for loss and five pass breakups last year, and his 54 tackles were the most by an Alabama lineman since 2007. Allen, a 6-foot-3, 272-pound junior, is more of a pure end, and he had five sacks and 11 tackles for loss last year.

16. Marquis Haynes, Ole Miss. With senior C.J. Johnson shifting to linebacker, Ole Miss can rest easy knowing it still has Haynes up front to rush the passer. A three-star recruit, Haynes made an instant impact in a Freshman All-America season, leading a talented Rebels defense with 7 ½ sacks. He also forced three fumbles and finished with 31 tackles, and he should move into more of a full-time role as a sophomore, with the presence of Robert Nkemdiche next to him creating plenty of opportunities.

15. Ken Ekanem, Virginia Tech. The Hokies finished fourth in the nation in sacks last year, with Ekanem breaking into the starting lineup and quickly becoming one of the ACC's best pass rushers as a sophomore. He finished second in the conference with 10 ½ sacks, also posting 15 ½ tackles for loss and 54 tackles. While a shoulder injury sidelined him in spring practice, Ekanem will be ready to play a big role for a loaded Hokies defensive line that will be among the best in the country.

14. Carl Lawson, Auburn. A five-star recruit in 2013, Lawson made an early impact as a freshman on the Auburn team that went to the national title game. He finished with only four sacks, but he flashed a high ceiling that set him up for big things in 2014. Unfortunately, he tore his ACL last July, forcing him to sit out the season and watch as Auburn struggled to get after the quarterback. Now, his return is a real boon to new defensive coordinator Will Muschamp, who could shape Lawson into one of the nation's best pass rushers.

13. Hunter Dimick, Utah. Nate Orchard stole the show with 18 ½ sacks last year, but now that he's gone, it's Dimick's turn to shine. As a sophomore playing opposite Orchard, Dimick racked up 10 sacks, 14 ½ tackles for loss, 52 tackles and two forced fumbles, and now the 6-foot-3, 266-pound junior could become one of the Pac-12's most productive pass rushers, as the leader of what should be an excellent defensive front again.

12. Devonte Fields, Louisville. We haven't actually seen Fields play since 2012, when as a TCU freshman, he finished with 10 sacks and led the Big 12 with 18 ½ tackles for loss. A foot injury sidelined him for most of the 2013 season, and while hype built around him last year, he was kicked off the team after he was accused of assaulting his ex-girlfriend. He spent last year at Trinity Valley Community College and has now enrolled at Louisville. Last week, the misdemeanor assault charge was dismissed pending his completion of four anger management courses.

11. Shaq Lawson, Clemson. Clemson loses much of what was one of the best defensive fronts in the nation, including Vic Beasley and Grady Jarrett, but there are still experienced contributors returning in bigger roles. Most noteworthy is Lawson, a 6-foot-3, 275-pound junior who has seen plenty of snaps in the Tigers' rotation the last two years. He has 7 ½ sacks and 21 ½ tackles for loss total over the last two seasons, ranking second in both categories behind Beasley last year. Now, he has a chance to shine as the top player on the Clemson defensive front.

10. Pete Robertson, Texas Tech. A hybrid end/linebacker, Robertson will essentially be playing a standup rush end type position in new coordinator David Gibbs' 4-3 scheme. Whatever you want to label him, he's easily the best player on a defense in dire need of playmakers. The Red Raiders struggled to tackle and defend anything last year, but Robertson proved to be an explosive edge rusher, leading the Big 12 with 13 sacks and finishing with 82 tackles. He has room to grow against the run and will face questions about his size in the pros (6-foot-3, 238 pounds), but he's perhaps the Red Raiders' most valuable player after picking up more than half of the team's sacks in 2014.

9. Sheldon Rankins, Louisville. A hybrid end/tackle, the 303-pound Rankins had a breakout 2014 season as a defensive end in new coordinator Todd Grantham's three-man front. The Cardinals produced one of the nation's best defenses, and Rankings led the charge with a team-high eight sacks and 13 ½ tackles for loss, also finishing with 53 tackles, two interceptions and a forced fumble. While the arrival of Devonte Fields will bring attention, Rankins is a rising star and a physical, disruptive presence up front.

8. Dadi Nicolas, Virginia Tech. Nicolas has gradually grown into more than just a pass-rush specialist, although at 6-foot-4, 236 pounds that is what his game revolves around. In Bud Foster's creative scheme that brings pressure from all angles, Nicolas, a senior, is a valuable asset, bringing explosiveness off the edge of the Hokies defense. He had 8 ½ sacks, 18 tackles for loss and 71 tackles last season, and he could develop into a national star as a senior.

7. DeForest Buckner, Oregon. The towering 6-foot-7, 290-pound Buckner opted to return for his senior season after an impressive 2014 breakout in which he finished with a team-high 13 tackles for loss. Fellow Ducks end Arik Armstead was the more hyped player and ended up getting picked 15th overall in the draft, but Buckner's production has been better. A perfect fit as an end in Oregon's 3-4 scheme, Buckner also finished with 81 total tackles last season, showing off his impressive quickness and range for a man of his size.

6. Shilique Calhoun, Michigan State. Calhoun generated a lot of attention early in 2013 when he out-scored a struggling Spartans offense himself, with three defensive touchdowns in the team's first two games. It actually may have caused him to be a bit overrated at first, but he has grown into one of the nation's best defensive ends -- with plenty of untapped potential still. He returned for his senior season despite the loss of defensive coordinator Pat Narduzzi, after recording eight sacks and 12 ½ tackles for loss last year. He has the quickness and speed off the edge to help ease the transition of a new-look secondary behind him.

5. Myles Garrett, Texas A&M. The Aggies had plenty of problems on defense last year, but Garrett's instant impact as a freshman saved them from even more frustrations. He boosted a lackluster pass rush in a hurry, debuting with an SEC freshman record 11 ½ sacks and 53 tackles. Eight of those sacks did come against Lamar, Rice and Louisiana-Monroe, so there's plenty of room to grow against stiffer SEC competition, but the 6-foot-5, 255-pound sophomore clearly has top-end talent, with explosive burst off the line that will make him one of the nation's best pass rushers.

4. Derek Barnett, Tennessee. One of many rising young stars at Tennessee, Barnett starred as a freshman, posting 10 sacks and 20 ½ tackles for loss (second in the SEC) as he dominated SEC competition. Texas A&M's Garrett got more hype, but Barnett actually had the more impressive freshman season overall, although he got more help thanks to the presence of pass rusher Curt Maggitt opposite him. Barnett also had 72 tackles, proving to be a relentless force and perhaps already the best player for a Vols team that is quickly rising into SEC contention.

3. Emmanuel Ogbah, Oklahoma State. Ogbah broke out in last year's season opener against Florida State, and he quickly became one of the nation's most disruptive ends. Now a redshirt junior, the 6-foot-4, 275-pound Ogbah decided to return for a fourth season in Stillwater after earning first-team All-Big 12 honors with 11 sacks and 17 tackles for loss. A quick, physical end, Ogbah brings relentless energy off the end, and he still seems to be only scratching the surface, with a high ceiling in 2015.

2. Shawn Oakman, Baylor. Oakman has had a longer road to the top than other stars, as he began his career at Penn State, then transferred to Baylor, where he was originally a situational player. His journey still isn't complete, either: He returned for his senior season to continue to develop a more complete game, as he's still somewhat raw, technically speaking, and has work to do in the run game. With that said, he's No. 2 here for a reason. He's a 6-foot-9, 280-pound terror who had 11 sacks, 19 ½ tackles for loss and three forced fumbles last year, increasing his workload and becoming a dominant force because of his athleticism and physicality.

1. Joey Bosa, Ohio State. Bosa broke onto the scene as a freshman in 2013 and hasn't looked back. A freakish athlete at 6-foot-6, 275 pounds, Bosa is more than just a pass rusher, bringing a complete skill set that allows him to line up anywhere on the line, get after the quarterback, stuff the run and make disruptive plays in the backfield. Offenses always need to account for where he is, and they often wisely run away from him (see Alabama's game plan in the Sugar Bowl). In two seasons, he has 21 sacks and 34 ½ tackles for loss, and he also forced four fumbles last year. The best player on the nation's best team, Bosa is the early favorite to be the No. 1 pick in the 2016 NFL draft.

Honorable Mention (alphabetical order): Jonathan Bullard, Florida; Theiren Cockran, Minnesota; KeShun Freeman, Georgia Tech; Bronson Kaufusi, BYU; Alex McCalister, Florida; Silverberry Mouhon, Cincinnati; Yannick Ngakoue, Maryland; Thomas Niles, UCF; Mike Rose, N.C. State; Ian Seau, Nevada; K.J. Smith, Baylor; Charles Tapper, Oklahoma; Kemoko Turay, Rutgers; Jihad Ward, Illinois; Eddie Yarbrough, Wyoming

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Defensive Tackles

20. Davion Pierson, TCU. For all the justified hype around TCU and its loaded offense, there is plenty of work to be done with the turnover on defense. The line brings back the most experience, and it all starts with Pierson, a 6-foot-2, 305-pound senior who has started 35 games in his TCU career. He finished with only 30 tackles, eight tackles for loss and 3 ½ sacks last season, but he's a steady presence for the Horned Frogs, anchoring what is almost always a strong defensive front.

19. Hassan Ridgeway, Texas. It's now Ridgeway's turn for the spotlight. The Longhorns, despite their struggles, played excellent defense most of last year under Charlie Strong, but they lose many key players -- including end Cedric Reed and tackle Malcom Brown, a first-round pick. With both gone, it's Ridgeway's turn to become a star up front. A 6-foot-4, 307-pound junior, Ridgeway started the final 10 games last year, finishing with 9 ½ tackles for loss, six sacks and 46 tackles.

18. Austin Johnson, Penn State. Johnson doesn't get the accolades of teammate Anthony Zettel, but his ability to anchor the defensive line and occupy blockers helped free up phenomenal production around him. Penn State continues to churn out strong defenses, and Johnson helped lead a unit that ranked second nationally against the run, allowing only 2.95 yards per carry. With 49 tackles and six tackles for loss it's harder for Johnson to get recognition, but the 325-pound senior makes life much easier for Zettel up front, in addition to having the athleticism to make his own plays and collapse the pocket.

17. Darius Hamilton, Rutgers. One of the best recruits in Rutgers history in 2012, Hamilton made an immediate impact and has been a full-time starter the last two years. While he's only 6-foot-4, 255 pounds, Hamilton has excelled as a defensive tackle, bringing phenomenal quickness to the position. He led the Scarlet Knights with 11 ½ tackles for loss last year, finishing with six sacks and 45 tackles. The Rutgers run defense has struggled, but Hamilton's disruption up front makes him the defense's most valuable player, by far.

16. Chris Jones, Mississippi State. After flashing big-time talent as a freshman in 2013, Jones didn't quite have the national breakthrough expected last season, despite the success of the team as a whole. Part of the reason was the competition around him, as the Bulldogs boasted a formidable defensive front. He didn't start a game, and he finished the season with 26 tackles and three sacks as a rotational player. Now's the time for the real breakout, as the Bulldogs lose five starters in their front seven, including both tackles. Jones, a 6-foot-5, 308-pound junior, was a five-star recruit out of high school, and he's embracing the high expectations that come with moving into the starting lineup.

15. Gerrand Johnson, Louisiana-Monroe. While listed at just 6-foot, 280 pounds, Johnson has dominated Sun Belt competition, starting 35 games in his career as a disruptive force at nose tackle for the Warhawks. Nose tackles rarely rack up big numbers, yet he somehow led ULM with 92 tackles last year, finishing with 12 ½ tackles for loss and 6 ½ sacks. He's quick and instinctive, and he sheds blocks well to wrap up ball carriers.

14. Eddie Vanderdoes, UCLA. A 6-foot-3, 305-pound junior, Vanderdoes has teamed with Kenny Clark to give the Bruins an exceptional pair of tackles to lead the defensive front. He had 50 tackles, 5 ½ tackles for loss and two sacks last year, and he even rushed for a touchdown against Utah. A five-star recruit out of high school, Vanderdoes initially signed with Notre Dame, but he changed his mind and ended up at UCLA, where he's made an impact since day one in 2013.

13. Adam Gotsis, Georgia Tech. A 6-foot-5, 282-pound senior from Australia, Gotsis emerged as an impact player with 14 ½ tackles for loss in 2013, then became the focal point of opposing offenses as a junior last year. The attention resulted in diminished stat-sheet production with 36 tackles and 6 ½ tackles for loss, but that doesn't mean he didn't make a significant impact. Given his relative inexperience in American football, he still has plenty of room to grow as he refines his game.

12. Luther Maddy, Virginia Tech. Maddy entered 2014 with high hopes, but unfortunately his senior season was derailed by a torn meniscus. He played in only four games before sitting out the rest of the way and seeking a redshirt. Previously, he established himself as one of the nation's most disruptive tackles, with 13 ½ tackles for loss, 55 tackles and 6 ½ sacks as a junior in 2013. He'll return to what should be a dominant defensive line that also features Dadi Nicolas, Corey Marshall, Nigel Williams and Ken Ekanem.

11. Lowell Lotulelei, Utah. The brother of former Utah tackle and first-round pick Star Lotulelei, Lowell Lotulelei is quickly making a name for himself. He started the final nine games for a stingy Utah defense last year as a freshman, sliding in at nose tackle at 6-foot-2, 310 pounds. He had 33 tackles, four sacks and a forced fumble, helping to eat up space in the middle of the defense to free up one of the nation's best pass rushes. His best game of his debut season actually came against Oregon, with 6 tackles and two sacks.

10. Harold Brantley, Missouri. The Tigers keep churning out quality defensive linemen, and while Kony Ealy, Shane Ray, Michael Sam and Markus Golden have stood out as ends, the tackle play has also been strong. Sheldon Richardson, of course, was taken in the first round of the 2013 draft, and now it's Brantley's turn to step up and anchor the line, especially with the attrition at end. The 280-pound junior started six games as a freshman in 2013, then picked up 54 tackles and five sacks in 10 starts last year. Not only is he a standout defensive tackle, but he's become something of a fake punt aficionado.

9. Kenny Clark, UCLA. The UCLA linebackers have gotten the most attention on defense lately -- and Myles Jack still is the standout -- but Clark anchors the defense at nose tackle, plugging the middle of the field and opening the door for production from those around him. A 6-foot-3, 308-pound junior, Clark emerged as a standout last year, teaming with Eddie Vanderdoes to form a stellar tackle combination for what will be one of the Pac-12's best defenses. Clark finished with 57 tackles and 5 ½ tackles for loss last year.

8. Sheldon Day, Notre Dame. An explosive player, Day can line up anywhere on the Fighting Irish defensive line, with a 6-foot-2, 285-pound frame and impressive power and quickness. A senior, Day isn't totally consistent yet, and last year a knee sprain limited him late in the season. In 11 games, he had 7 ½ tackles for loss, 40 tackles and a sack, and returning for his senior season was probably the right call. With a deeper Notre Dame defense in year two of coordinator Brian VanGorder's scheme, Day has an opportunity to develop into a star.

7. Montravius Adams, Auburn. Like Carl Lawson, Adams came to Auburn as a five-star recruit in 2013, and he made his presence felt early. He didn't start as a freshman, but he made an impact, and last year as a sophomore he started 10 games, recording eight tackles for loss, three sacks, 43 tackles and an interception. The 6-foot-4, 296-pound Adams has yet to reach his full potential, but he's a disruptive, versatile player who has played some defensive end as well. He could be primed for a breakout, especially if the pass rush improves around him as Lawson returns from his injury.

6. Adolphus Washington, Ohio State. A five-star defensive end out of high school listed at 230 pounds, Washington -- now 6-foot-4 and 290 pounds -- transitioned to tackle as a sophomore, becoming a full-time starter last year as a junior. Amazingly, he was one of the few eligible underclassmen on the Buckeyes who had to make an NFL decision, and he decided to return for his senior season. Last year, he played primarily on the nose and recorded 10 ½ tackles for loss, 4 ½ sacks and 48 tackles, but this year, with Michael Bennett gone, he'll move to the three-technique, which should be a more natural fit.

5. Maliek Collins, Nebraska. While the enduring image of the 2014 Cornhuskers defense is its part in allowing Melvin Gordon to run for 408 yards in three quarters, that shouldn't overshadow just how good Collins is capable of being. The 6-foot-2, 300-pound Collins brings explosiveness and quickness to the interior of the Nebraska defense, succeeding in breaking into the backfield and crashing the pocket. As a sophomore, he had 45 tackles, 10 ½ tackles for loss and 4 ½ sacks, and he's the best building block for Mike Riley's new regime in trying to plug the holes we saw last year on defense.

4. Andrew Billings, Baylor. While Shawn Oakman gets all the accolades, Billings has quietly developed into a force on the interior for the Bears, who keep getting better and better on defense. Like Oakman, Billings is a freakish athlete, a 6-foot-2, 300-pound junior who has phenomenal quickness and burst for his position. He was also a record-breaking state powerlifting champion in high school, and that strength shows on the field, where he played a huge role in a defense that allowed only 3.15 yards per carry, finishing with 11 ½ tackles for loss.

3. A'Shawn Robinson, Alabama. A versatile 312-pound junior, Robinson can line up anywhere on the Bama line, whether it's at end or nose tackle in the Tide's three-man front. He had 6 ½ tackles for loss and 49 tackles last year, but his impact was much greater than that, as he takes up blockers and moves very well for a player of his size. He can do whatever Alabama needs him to do, clogging the middle against the run or collapsing the pocket as a pass rusher. He's been an impact player since the day he set foot on Alabama's campus, as he had 5 ½ sacks as a freshman.

2. Anthony Zettel, Penn State. Originally a defensive end, the 6-foot-4, 278-pound Zettel may be somewhat undersized to play on the interior, but it doesn't matter. When he's not tackling trees, he's wreaking havoc on opposing backfields. In his first year as a starter, he finished second in the Big Ten with 17 tackles for loss, also posting eight sacks, three interceptions (one returned for a touchdown), 42 tackles and a forced fumble. He's freakishly quick and strong on the interior, and he sets the tone for everything Penn State's defense does under coordinator Bob Shoop, leading the charge for what was one of the best defenses in the nation. He's too quick for most interior offensive linemen to handle, and thus he's constantly helping to knock offenses off schedule and collapse the pocket on frustrated quarterbacks.

1. Robert Nkemdiche, Ole Miss. Consistency remains an issue with Nkemdiche, but otherwise he's on the verge of becoming, as advertised, the No. 1 overall recruit from the class of 2013. He shifted inside from defensive end to tackle as a freshman, although he has the versatility to line up anywhere up front for the Rebels. He's a powerful athlete at 6-foot-4, 296 pounds (here's a video of him rushing for a touchdown in high school), combining strength and quickness to get off the line in a hurry and generate pressure up the middle. His stats don't say that he's been dominant, with 35 tackles, four tackles for loss and two sacks last year, but he's clearly flashed big-time potential and opens the door for teammates to make plays around him. At his best, there's nobody better at the position.

Honorable Mention (alphabetical order): Josh Augusta, Missouri; Travis Britz, Kansas State; Tylor Harris, Wake Forest; Matt Ioannidis, Temple; Jarron Jones, Notre Dame; Orion Jones, Toledo; Christian LaCouture, LSU; Nile Lawrence-Stample, Florida State; Corey Marshall, Virginia Tech; Malik McDowell, Michigan State; Derrick Mitchell, Florida State; D.J. Reader, Clemson; Tashon Smallwood, Arizona State; Josh Tupou, Colorado; Vincent Valentine, Nebraska; Antwaun Woods, USC; Connor Wujciak, Boston College

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