This offseason, we've ranked all the best college football players individually, and we've ranked the best position units. Now that it's August and we're preparing for our overall preseason rankings, it's time to take a look at the best offenses and defenses in college football.

First, it's the top 25 offenses, based on a combination of proven talent and coaching and how well we think these units will function as a whole during the 2017 season. (They're not necessarily rankings of who will score the most points or rack up the most yards.)

The top 25 defenses can be found here.

1. Oklahoma. On one hand, Oklahoma lost 2,334 combined rushing yards from Samaje Perine and Joe Mixon, and it lost 159 combined catches from Mixon, Perine, Geno Lewis and Heisman finalist Dede Westbrook. On the other hand, quarterback Baker Mayfield returns after his second straight top-four Heisman finish, and left tackle Orlando Brown leads a veteran offensive line that may be the best in the country. Offensive coordinator Lincoln Riley, one of the nation's top play-callers, was elevated to head coach, and while he has substantial production to replace, the foundation is here with Mayfield and a potentially dominant line, and there are plenty of breakout candidates at running back and receiver. The Sooners finished second in offensive SRS, first in Football Outsiders' offensive S&P+ and first among Power Five teams in yards per play. Maybe they won't match the highs of last year, when they went unbeaten in Big 12 play, but they can still be as dangerous as any offense in the country in the final year of the prolific Riley-Mayfield partnership.

2. Penn State. The Nittany Lions vaulted from 78th to 21st in yards per play, growing into an explosive big-play unit under new coordinator Joe Moorhead. Saquon Barkley is the nation's best running back, Trace McSorley averaged 9.3 yards per attempt in his first year starting at quarterback, the receiving corps will be deep even without Chris Godwin and the offensive line will easily be in its best shape since James Franklin arrived, with long-awaited depth. Penn State underwent a stunning transformation over the course of last season after a couple years of frustration, as the Lions emerged as one of the most entertaining teams in football. Most of that offense is back, with a year of familiarity in the system under their belts. Maybe they won't hit as many big plays, but they're going to be more efficient thanks to improved blocking.

3. Oklahoma State. Just about everything is in place for this to be one of the most explosive offenses. Mason Rudolph threw for 4,091 yards last year and is one of the nation's best passers. Justice Hill broke out as a freshman tailback, enlivening the Cowboys' ground game with 1,142 yards. The receiving corps returns All-American James Washington plus Jalen McCleskey and Chris Lacy, and it adds veteran Marcell Ateman, who missed 2016 with an injury, and LSU transfer Tyron Johnson. The line is the weakest unit here, but there's solid experience, and the Cowboys brought in Cal grad transfer Aaron Cochran to fill the void at left tackle. An NFL prospect QB is throwing to the nation's best receiving corps, making this a difficult offense to slow down.

4. USC. The Trojans have to replace three starters on the offensive line, and they have to replace top receivers JuJu Smith-Schuster and Darreus Rogers. There are hurdles for this offense to overcome in Sam Darnold's second season as starting quarterback, but Darnold has rightfully earned a wave of attention as the next big thing at the position. He threw for 3,086 yards and 31 TDs despite not starting the first three games in 2016, and he's shown plenty of great traits -- throwing under pressure, mobility, arm strength -- to make him a top Heisman candidate. He has an explosive running back in Ronald Jones II, and USC has recruited well enough to inspire confidence that the line and receiving corps (where Deontay Burnett is emerging as a star) will turn out just fine.

5. Alabama. There's no doubt that this offense has the talent to be one of the best in the country. It's a matter of expanding the passing game under new coordinator Brian Daboll in QB Jalen Hurts' second year as starter after he won the job -- and was named SEC offensive player of the year -- as a true freshman. A limited passing attack hurt the Tide on third down against good defenses, as we saw in the playoff, but Hurts has plenty of weapons around him. That includes an absurdly deep running back corps led by Bo Scarbrough, and options at receiver led by Calvin Ridley. Throw in one of the nation's top lines, and this offense is in excellent shape, even if there are flaws that need to be fixed.

6. Washington. As a head coach, Chris Petersen's first six offenses at Boise State finished in the top 16 nationally in yards per play. The Broncos' offense fell off his final two years there, and the first two years at Washington continued that trend. Last year, however, Petersen recaptured former magic: Washington finished 10th in yards per play and scored 41.8 points per game, with a spectacularly efficient season from QB Jake Browning until he hurt his shoulder in November. The Huskies lose speedy John Ross, but a healthy Browning paired with a veteran line, a terrific one-two punch at tailback in Myles Gaskin and Lavon Coleman and a receiving corps that's still in good shape, headlined by Dante Pettis, sets up this team for big things again.

7. Louisville. Can Louisville adequately protect Lamar Jackson? He won the Heisman with 5,114 yards of total offense and 51 total TDs despite having subpar blocking in front of him -- a problem that caused the Cardinals to unravel in late-season losses to Houston and LSU. Jackson also loses top tailback Brandon Radcliff and his top three receivers, but despite all the questions, the Cards have a great offensive coach, Bobby Petrino, with a third-year Heisman winner at QB. Improve the line, and an offense with more refined passing from Jackson will continue to put up big numbers overall, although defenses in the ACC will provide many challenges this season.

8. Oregon. The Ducks had problems on the offensive line and switched to a freshman quarterback in the middle of last season, and yet they still ranked 18th in yards per play. Offense wasn't the problem, and offense certainly won't be a problem in Willie Taggart's first season. Left tackle Tyrell Crosby is back from injury to lead a more experienced line. A healthier Royce Freeman leads a deep group of running backs. And Justin Herbert showed lots of positive signs in his first year at QB. Finding weapons on the perimeter is the key after top receiver Darren Carrington was kicked off the team this summer, but there's going to be explosiveness here, led by what can be a dominant rushing attack.

9. Ohio State. The Buckeyes have gone 23-3 without Tom Herman, but his absence has been felt through inconsistent offensive performances the past two years, capped by the shutout loss to Clemson in the playoff. Urban Meyer brought in ex-Indiana head coach Kevin Wilson, whose addition should be immediate dividends as offensive coordinator. The key is finding new weapons in the receiving corps, improving in pass protection in big games and stretching the field. J.T. Barrett has done big things in his Ohio State career, but he averaged only 6.7 yards per attempt last year. The talent is here; the Buckeyes need to find an identity again and develop some explosiveness, especially with Curtis Samuel gone, after finishing 47th in yards per play.

10. Florida State. Pass protection remains a major question mark, especially for a team that has to play against Alabama, Miami, N.C. State, Clemson and Florida. Deondre Francois was hit a lot as a freshman starter, and while he gets some of the blame, there's no doubt that the Florida State offensive line needs improvement. Francois otherwise had a terrific debut, throwing for 3,350 yards and 20 TDs, and despite the loss of Dalvin Cook, the running game should be fine with junior Jacques Patrick and touted true freshman Cam Akers. Francois needs more help from his line, and he needs receivers like Auden Tate and Nyqwan Murray to emerge as go-to playmakers. Despite the question marks, there's plenty of talent for Jimbo Fisher to work with as FSU pursues a playoff bid.

11. Texas Tech. The Red Raiders are going to score a ton of points. We know this; the offense's success is as predictable as the defense's struggles. Replacing Patrick Mahomes at QB won't be easy -- and the transfer of top WR Jonathan Giles hurts -- but new QB Nic Shimonek will undoubtedly put up enormous numbers in Kliff Kingsbury's offense, and Texas Tech will be a safe bet to roll up a lot of points most weeks. Nearly all of Texas Tech's worries reside on the other side of the ball, again.

12. Auburn. Gus Malzahn has been offensive coordinator (2009-11) or head coach (2013-16) of Auburn for seven years. Here's the progression of offensive SRS ratings, via Sports-Reference: sixth, first, 38th, third, seventh, 49th, 78th. The hope is that Baylor transfer QB Jarrett Stidham, emerging young talent at receiver and the addition of new offensive coordinator Chip Lindsey can snap this offense out of its funk and expand the passing game. We know the Tigers will be able to run with a stellar line paving the way for Kamryn Pettway and Kerryon Johnson. If Stidham comes close to living up to increasingly high expectations, there's a high ceiling here for Auburn's offense as a whole.

13. Notre Dame. The Fighting Irish will try to bounce back from a strange 4-8 season with new coordinators, including Chip Long on offense to replace new WKU coach Mike Sanford. Redshirt sophomore QB Brandon Wimbush hasn't played much, but he steps into a promising situation despite all the drama in South Bend over the past year. The left side of the ND line, at least, is as good as any in the country, and Wimbush has a solid group of weapons to throw to, headlined by Equanimeous St. Brown. Junior Josh Adams leads a group of running backs bursting with potential, too. Wimbush is a great breakout candidate, and this offense can become dangerous again in a hurry.

14. Washington State. A limited number of big plays holds the Cougars back a bit -- they were 40th in yards per play -- but this is a Mike Leach Air Raid offense with an experienced, prolific quarterback in Luke Falk, who has over 10,000 career passing yards. The line is in good shape, led by guard Cody O'Connell, and Falk still has proven weapons despite losing Gabe Marks and River Cracraft. This could be Leach's best offense since taking the Washington State job.

15. Clemson. The Tigers have earned the benefit of the doubt on both sides of the ball, given how they've coached and recruited. There's no way to avoid taking a step back on offense this year without Deshaun Watson -- not to mention Wayne Gallman, Mike Williams, Jordan Leggett, Artavis Scott and Jay Guillermo -- but the receiving corps and offensive line still rank among the nation's best and there's potential in the backfield. The potential at quarterback might take a year to unlock -- Hunter Johnson was the nation's No. 2 QB recruit -- but there's enough here now to continue to make this an effective unit, even if a drop-off is inevitable.

16. South Florida. It's not hard to see why USF will be viewed as the consensus favorite for the Group of Five's major bowl spot. The Bulls went 11-2 last year, finishing 19th in the AP poll, and they return a talented playmaker at QB in Quinton Flowers, who had 2,812 passing yards, 1,530 rushing yards and 42 total TDs leading an offense that averaged 43.8 points per game. He should fit in well with new coordinator Sterlin Gilbert under Charlie Strong. The staff change combined with the losses of RB Marlon Mack and WR Rodney Adams could cause the Bulls to take a slight step back on offense, but enough pieces are in place for this to be among the nation's most explosive units, one that will put up huge numbers against a weak schedule.

17. Kansas State. The Wildcats weren't particularly intimidating on offense last year, but they finished strong and return eight starters, including a newly healthy Jesse Ertz at QB. Ertz rushed for over 1,000 yards despite dealing with a shoulder injury that required surgery after the season. He has a rock-solid line in front of him, led by Dalton Risner, and there are some promising weapons, led by Byron Pringle and Alex Barnes. As David Ubben wrote, Bill Snyder often does big things with experience at quarterback, so this could become a dangerously efficient and effective unit.

18. Ole Miss. Offensive line coach Matt Luke takes over as head coach after Hugh Freeze's ouster, and the Rebels also have a new offensive coordinator in Phil Longo, who comes in from San Houston State. Longo takes over a unit with a ton of potential despite the program's overall turmoil. Sophomore QB Shea Patterson was the No. 1 QB recruit in the class of 2016, and he's throwing to a receiving corps loaded with upside thanks to blue-chip recruits A.J. Brown, D.K. Metcalf and Van Jefferson. While the running game is an issue, Patterson could have a big season, statistically, if he develops as hoped.

19. TCU. The Horned Frogs were all over the map last season, stumbling to a 6-7 record that featured inconsistent performances -- like scoring 62 points against Baylor one game, then six points against Oklahoma State the next. While Kenny Hill has yet to become a truly reliable quarterback, he's in a good spot here, with almost everyone back around him. That included a standout tailback in Kyle Hicks, a veteran offensive line and a deep receiving corps led by KaVontae Turpin, Taj Williams and John Diarse. Sonny Cumbie will take over as the lead play-caller with Doug Meacham gone, and the Horned Frogs are built for a bounce back on offense after a frustrating first year without Trevone Boykin.

20. Texas. Tom Herman has proven to be one of college football's finest offensive minds, and despite all the problems that Texas had in recent years, it's not as if the cupboard is bare on offense. Shane Buechele had predictably mixed results as a freshman QB, but if he holds onto the job, he's in a good position to succeed. Connor Williams leads an experienced line, and the receiving corps has rising talent, led by Devin Duvernay. While 2,000-yard rusher D'Onta Foreman will be missed, Chris Warren has flashed potential when healthy. Texas isn't going to be a powerhouse immediately, but a rebuild to respectability and watchability can happen relatively quickly.

21. West Virginia. The Mountaineers may get an upgrade at quarterback in Will Grier, a transfer from Florida, and senior RB Justin Crawford ran for 1,184 yards as a juco transfer last fall. Only five starters return on offense -- center Tyler Orlosky and receivers Shelton Gibson and Daikiel Shorts are among the impact players lost -- but Grier offers hope that Dana Holgorsen's offense can perform at a high level, which is a necessity, given the greater attrition facing the defense.

22. LSU. Stagnant offensive philosophies combined with mediocre quarterback play doomed the Les Miles era, but the Tigers' offensive problems have sometimes been overstated. They recruit so well that there's always talent; it just hasn't always been deployed or developed properly. With the help of fantastic running backs, LSU has ranked in the top 20 in yards per play each of the past two years and was 22nd in Football Outsiders' S&P+ offensive ratings in 2016. Ed Orgeron made a great hire in offensive coordinator Matt Canada, a creative play-caller who quickly made Pitt into one of the nation's top offenses last year. At LSU, Canada inherits star tailback Derrius Guice, a quality offensive line (although the suspension and impending transfer of guard Maea Teuhema hurts) and a serviceable QB in Danny Etling, with a few promising weapons like D.J. Chark. Don't let the results against Alabama completely define how this offense has performed.

23. Memphis. The Tigers lost coach Justin Fuente and first-round QB Paxton Lynch, and yet they still scored 38.8 points per game in an eight-win season that included a 48-44 win over Houston to close the regular season. Head coach Mike Norvell lost offensive coordinator Chip Long to Notre Dame, but he has back most of the rest of the offense, headlined by QB Riley Ferguson, who threw for 3,698 yards and 32 TDs, and standout WR Anthony Miller, who had 95 catches. USF is getting all the attention in the American, but Memphis is going to be a lot of fun, too.

 24. Colorado State. The Rams are overshadowed in the Mountain West's Mountain Division by Boise State and Wyoming QB Josh Allen, but they emerged as a dangerous offense in the second half of last season, scoring at least 37 points in each of their final six games. QB Nick Stevens put up big numbers down the stretch, and all of Colorado State's top skill players are back, led by prolific receiver Michael Gallup. The Rams ended up 32nd in offensive SRS and 21st in offensive S&P+, and they're Mountain West contenders.

25. Mississippi State. This spot almost went to Missouri, which returns everybody from a much-improved unit, but Mississippi State has the QB edge. The Bulldogs scored at least 35 points in four of their last five SEC games -- the exception, predictably, being Alabama -- as they found a new standout QB in Nick Fitzgerald. Fitzgerald won't reach the same heights that Dak Prescott did, but he rushed for 1,375 yards and 16 TDs and passed for 2,423 yards and 21 TDs as a sophomore first-year starter. Dan Mullen is a proven quarterbacks coach, and how high this offense rises depends on reloading the offensive line -- although Martinas Rankin is a rising star -- and replacing top receiver Fred Ross.

Top 25 defenses

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