Here is part five of our preseason power rankings at each position.
We will update the power rankings each week during the regular season and release the final rankings for the season after the BCS title game.
The rating of a player and coach can fluctuate each week during the season depending on how they fared the previous week, but the power rankings measure overall career performances as well as their most recent results.
Here are the nation's top 20 defensive ends. Next up: defensive tackles.
DEFENSIVE END POWER RANKINGS
1. Adrian Clayborn, Iowa (6-4/285, Sr.) BUZZ: Clayborn is heading into his third season as a starter for the defense-minded Hawkeyes. He had 70 tackles last season, including 11.5 sacks and 20 tackles for loss. He also had four forced fumbles and nine quarterback hurries. He was MVP of Iowa's Orange Bowl win over Georgia Tech, with nine tackles and two sacks.
2. Robert Quinn, North Carolina (6-5/270, Jr.) BUZZ: Quinn had surgery for a benign brain tumor as a senior in high school, but he has been a starter for the Tar Heels since his true freshman season in 2008. He led the ACC in tackles for loss (19) and placed second in the conference in sacks (11) last season. Quinn also forced six fumbles to rank fourth in the nation in that category.
3. Greg Romeus, Pittsburgh (6-6/270, Sr.) BUZZ: He finished last season with eight sacks on a team that led the nation in that category. Romeus was more of a basketball player in high school, and played just one season of high school football. But Romeus has developed into one of the nation's top ends and is considered a likely first-round pick.
4. Ryan Kerrigan, Purdue (6-4/263, Sr.) BUZZ: Kerrigan enjoyed a breakout season in 2009 by leading the Big Ten and ranking third in the nation with 13 sacks. Kerrigan ranked fourth in the Big Ten with 18.5 tackles for loss en route to earning first-team All-Big Ten honors. He also has forced nine fumbles and is the current career leader in that category nationally.
5. Cameron Heyward, Ohio State (6-5/288, Sr.) BUZZ: The son of the late Craig "Ironhead" Heyward, Cameron appears primed for a huge senior season. He stepped into the Buckeyes' starting lineup as a true freshman in 2007 and hasn't left. He possesses outstanding quickness and athletic ability. Heyward, who also has played tackle, had 6.5 sacks and 10 tackles for loss last season.
6. Marcell Dareus, Alabama (6-4/306, Jr.) BUZZ: Even though he made only four starts last season, Dareus delivered a team-high 6.5 sacks. He also delivered the hit that knocked Texas quarterback Colt McCoy out of the BCS championship game and later scored on a 29-yard interception return. He was named defensive MVP of the BCS championship game.
7. Jeremy Beal, Oklahoma (6-3/267, Sr.) BUZZ: Beal has made 19.5 sacks and 34.5 tackles for loss over the past two seasons while earning first-team All-Big 12 honors in each of those seasons. He also was named a third-team All-American by The Associated Press last season. Beal is more than a pass-rushing specialist, as he has made 131 tackles in the past two seasons.
8. Kenny Rowe, Oregon (6-3/232, Sr.) BUZZ: Rowe had 11.5 sacks last season and led the Pac-10 and tied for ninth in the nation in sacks per game. He delivers some of his biggest performances in Oregon's biggest games. Last season, he recorded three sacks in the Rose Bowl and produced two sacks each against Boise State, California and UCLA.
9. Cliff Matthews, South Carolina (6-4/268, Sr.) BUZZ: Matthews had seven sacks and four forced fumbles last season to earn second-team All-SEC honors from the league's coaches. He had two sacks and forced and recovered a fumble in a win over Ole Miss, ranked fourth in the nation at the time. He also preserved a win over Kentucky by batting down a two-point conversion attempt that would have tied the game.
10. Da'Quan Bowers, Clemson (6-4/280, Jr.) BUZZ: Perhaps the most highly touted recruit ever to sign with Clemson, Bowers has made 105 tackles in his first two seasons despite dealing with nagging injuries. His 11-tackle effort against Georgia Tech in last season's ACC championship game suggests his best performances still are ahead of him.
11. Allen Bailey, Miami (6-4/285, Sr.) BUZZ: A beast in the weight room, Bailey is just as powerful on the field. He has split time at tackle and end, but figures to move to the edge full time this season. Last season, he led all Hurricanes linemen with 34 total tackles and topped the team with 11 tackles for loss, including seven sacks. A first team All-ACC selection, Bailey forced two fumbles in '09 and played his best football in the second half of the season.
12. Aldon Smith, Missouri (6-5/250, Soph.) BUZZ: He made a huge impact in his first season and aims to take his performance to another level. Last season, Smith, a relentless and athletic pass rusher, was an obvious choice for Big 12 defensive freshman of the year and Freshman All-America honors after setting a Missouri single-season record with 11.5 sacks. He had 64 tackles, with 19 for loss.
13. Sam Acho, Texas (6-3/260, Sr.) BUZZ: He's expected to follow Brian Orakpo and Sergio Kindle as the Longhorns' next dominant pass-rushing end. He actually established himself in a breakout year last season in which he posted 63 tackles and 10 sacks. He also was credited with 15 quarterback pressures. Acho will move inside to tackle in some situations to allow the Longhorns to bolster their pass rush.
14. Ryan Winterswyk, Boise State (6-4, 263, Sr.) BUZZ: Perhaps one of the country's most under-appreciated players, Winterswyk is a productive pass rusher and solid lineman. A two-time All-WAC selection, he's coming off a strong junior season in which he recorded nine sacks and 17 tackles for loss. He was a key figure in the Broncos' ranking 14th in the nation in total defense last season.
15. Bruce Miller, UCF (6-2/253, Sr.) BUZZ: The nation's current career leader in sacks, with 27? It's this guy. He's not overly big, but he is speedy off the edge and relentless. He had 13 sacks last season, with another seven quarterback hurries. He had multiple sacks in four games. His career high of three sacks in a game came in 2008 against Miami.
16. Pernell McPhee, Mississippi State (6-4/285, Sr.) BUZZ: A late bloomer who only played one season of high school football in Pahokee, Fla., McPhee quickly has made up for lost time. Twice a junior college All-America, he received All-SEC recognition last season after posting 52 tackles, including 12 tackles for loss and five sacks. He had 11 tackles, 3.5 for losses, and a sack against Georgia Tech.
17. Kentrell Lockett, Ole Miss (6-5/260, Sr.) BUZZ: Lockett's quotes and tweets on Twitter attract a lot of attention. So does his play. He was selected to some All-SEC teams after a solid junior season in which he posted five sacks and was credited with 13 pressures. Overall, Lockett had 39 tackles, with 10 going for lost yardage.
18. Julian Miller, West Virginia (6-4/260, Jr.) BUZZ: A year ago, Miller emerged as a force with which to be reckoned in the Big East. He posted nine sacks for 61 yards in losses, recorded 53 tackles (30 unassisted) and broke up three passes en route to gaining All-Big East recognition. This season, he has said he'll be embracing a leadership role for the Mountaineers. He figures to be embracing a lot of quarterbacks, too.
19. Adrian Robinson, Temple (6-2/250, Jr.) BUZZ: Robinson was named the MAC's Defensive Player of the Year last season after posting 46 tackles and 13 sacks. He also ranked among the nation's top 10 in forced fumbles with five. He's almost as consistent as he is relentless. Robinson, who has a great first step, either posted a sack or assisted on one in 10 games last season. He had two tackles for loss and a sack against UCLA in the EagleBank Bowl.
20. Ricky Elmore, Arizona (6-5/250, Sr.) BUZZ: Injuries to fellow end Brooks Reed could have severely weakened Arizona's defense last season had Elmore not emerged as a pass-rushing threat. Elmore led the Wildcats and was third in the Pac-10 with 10.5 sacks among his 44 tackles. He'll be a strong contender for all-league honors this season.