X factor for each Top 25 team down the stretch

Michigan's defense will test Barkley (1:23)

Penn State running back Saquon Barkley has emerged as one of the best players in college football, but Saturday he'll have his toughest test yet when the Nittany Lions take on the Wolverines. (1:23)

We know the impact players such as Baker Mayfield and Bryce Love have on their respective team's success. Who are the less obvious players, the position units or the coordinators who will be key for each Top 25 team in the second half of the season?

1. Alabama: RB Josh Jacobs

Alabama coach Nick Saban has said he wants to get Jacobs, the third running back on the depth chart, more involved in the offense. He has missed three games and has only 124 rushing yards on the season. Still, he's averaging 7.8 yards per carry, and in a league that prides itself on multi-back running systems, Alabama doesn't have to compromise playcalling when Jacobs is in. -- Edward Aschoff

2. Penn State: Offensive coordinator Joe Moorhead

Moorhead's creativity will be put to the test in the next couple of weeks. How many new, interesting ways can he find to get the ball in tailback Saquon Barkley's hands? Some teams have been able to hold Barkley at bay in the ground game. With Michigan and Ohio State as their next two opponents, what kind of counterpunches do the Nittany Lions have in their repertoire? -- Dan Murphy

3. Georgia: DT Trenton Thompson

Georgia's rushing defense ranks fifth in the country, allowing 82.1 yards per game, but a healthy Thompson will only reinforce the Bulldogs' strength in the trenches. He has missed the past two games with a sprained MCL, but appears to be on track to play against Florida next week. He's Georgia's top defensive lineman and his return will only make this line tougher against better rushing offenses -- like Auburn and Georgia Tech -- down the stretch. -- Aschoff

4. TCU: WR KaVontae Turpin

After a quiet start to Big 12 play, Turpin finally broke out against Kansas State with five receptions and 70 yards. Turpin has demonstrated the ability in the past to be a game-breaker at receiver and on special teams, and will be key to TCU's playoff hopes. -- Jake Trotter

5. Wisconsin: Turnovers

Lesser opponents have hung with the Badgers in recent weeks by taking the ball away (Purdue and Northwestern each had three). If Wisconsin quarterback Alex Hornibrook and his offense are going to make a run at a championship this season, they won't be able to give more talented teams the same opportunities. -- Murphy

6. Ohio State: QB J.T. Barrett

Barrett's chance to win some big ones has arrived. The veteran quarterback is once again putting up gaudy numbers against the teams Ohio State should beat, with 22 total touchdowns and no interceptions in five games since the loss to Oklahoma. He can cement his legacy as an all-timer by proving he can make clutch plays in the close games, too. -- Murphy

7. Clemson: RB Travis Etienne

He has just 51 carries in six games played, but Etienne has clearly established himself as one of the country's most explosive runners. The true freshman has four carries of 50 yards or more, scoring six touchdowns and leading the Tigers in rushing yards. The problem, however, is that Etienne is still a work in progress in pass protection, and has had some notable misses in blitz pickup. That makes him a liability in passing situations, giving Clemson's offensive staff a big question to grapple with: explosiveness in the ground game, or consistency in pass protection? -- David M. Hale

8. Miami: WR Ahmmon Richards

Richards, last season's leading receiver, has dealt with a hamstring injury for the majority of the season, playing in only two games. That has meant more opportunities for Darrell Langham, and he has come through in a big way. Langham has emerged the past two weeks as the most clutch receiver on the team, and finding more options at receiver can only help as the Hurricanes make their push for the ACC title. -- Andrea Adelson

9. Oklahoma: RB Trey Sermon

The true freshman has been carrying a big chunk of the rushing load for the Sooners, who lost a pair of 1,000-yard rushers off last season's team in Joe Mixon and Samaje Perine. With 469 yards, Sermon will have a chance to become just the fourth Oklahoma running back to rush for more than 1,000 yards as a true freshman. -- Trotter

10. Oklahoma State: WR Marcell Ateman

James Washington rightfully garners the headlines, but Ateman is also having a monster season for the Pokes. According to ESPN Stats & Information research, Washington and Ateman are the first teammates with four-game streaks of 100 yards receiving at the same time since at least 2004. They're also both tied for the nation's longest active streaks. -- Trotter

11. USC: WRs Steven Mitchell Jr., Tyler Vaughns

For USC quarterback Sam Darnold, receiver Deontay Burnett (49 catches, 626 yards) is the clear No. 1 option. What the Trojans need is reliable production beyond him. Mitchell Jr. and Vaughns (48 catches, 620 yards combined) will both be key as USC tries to remain in the playoff picture. -- Kyle Bonagura

12. Washington: RB Lavon Coleman

With Myles Gaskin and Coleman, Washington figured to have one of the best running back tandems in the country this season, but they haven't quite produced at last year's level. There are various reasons for that, but a big second half from Coleman (42 carries, 200 yards) would help give the Huskies more of a well-rounded offense. -- Bonagura

13. Notre Dame: QB Brandon Wimbush

Will Wimbush remain healthy enough to keep the Irish rushing attack humming at full speed? The threat of the quarterback run has helped keep defenses honest while Josh Adams and the rest of the Irish running backs have taken advantage. If Wimbush is durable enough to get through a gauntlet of ranked teams, Notre Dame could be headed toward double-digit wins. -- Murphy

14. Virginia Tech: RB Travon McMillian

For the Hokies to contend for the ACC Coastal Division, they need consistency from their running backs. They rank tied for 10th in the ACC in yards per carry (4.0). McMillian had a season-high 17 carries against Boston College, and could be in line for even more down the stretch. -- Adelson

15. Washington State: Offensive line

In the Cougars' shocking 37-3 loss to Cal, quarterback Luke Falk never got comfortable in the pocket and was sacked nine times. Cal's pass rush prevented him from finding any sort of a rhythm. No FBS team has allowed more sacks than Wazzu (32), and if it's going to contend for the Pac-12 title, the offensive line has to improve. -- Bonagura

16. (tie) NC State: RB Nyheim Hines

Amid the hype over defensive end Bradley Chubb, quarterback Ryan Finley's streak of 313 passes without an interception or tight end Jaylen Samuels' do-it-all attack, Hines is perhaps NC State's most overlooked star. Hines was dominant in the Wolfpack's most recent win against Pitt, rushing for 135 yards and a touchdown while returning a punt for another score. Hines is one of just nine players in the FBS with 1,000 all-purpose yards on the season. -- Hale

16. (tie) USF: The schedule

Yes, USF has been spectacular so far, but how much do we really know about the Bulls? USF's five FBS opponents are a combined 6-25 in FBS games this season and have been outscored by an average of 20 points per game. What happens when things get tougher, starting with Tulane this week? And with the Bulls missing Memphis, Navy and SMU, will there be a real challenge ahead of the season finale at UCF? -- Hale

18. Michigan State: Defensive front

The Spartans have held three of their first six opponents to under 75 rushing yards. No one has really threatened 200 on the ground against a young unit that was supposed to be a liability. Keep that up, and the Spartans will continue ascending in the Big Ten. -- Murphy

19. Michigan: RB Karan Higdon

Higdon had a career-high 200 yards rushing in an overtime win against Indiana. The junior could be the reliable force this offense needs to start constructing an identity to match its championship-caliber defense. -- Murphy

20. UCF: WR Otis Anderson

The Knights have the top scoring offense in the country thanks to the emergence of quarterback McKenzie Milton. Tre'Quan Smith leads all receivers, but UCF has started to rely more on true freshman Otis Anderson, who has contributed both as a rusher and receiver. Last week he got his first career start at receiver and finished with seven catches for 76 yards. -- Adelson

21. Auburn: QB Jarrett Stidham

Yes, Auburn coach Gus Malzahn wants to be a run-first team, but this offense doesn't strike fear in opponents unless there's a viable passing game to help open up the running game. Take the recent loss to LSU as an example. In the first quarter, Stidham completed 5 of 7 passes for 119 yards and a touchdown and Auburn scored 17 points. He was 4-of-19 passing for 46 yards and no touchdowns in the final three quarters as Auburn squandered a 20-point lead in a 27-23 loss. -- Aschoff

22. Stanford: QBs Keller Chryst, K.J. Costello

With the nation's leading rusher in Bryce Love, opposing defenses are going to keep trying to find ways to stop him. That's going to mean a lot of people in the box, leaving more opportunities for Chryst (and sometimes Costello) to make plays through the passing game. -- Bonagura

23. West Virginia: LB David Long

After missing the first four games of the season with a knee injury, Long has returned to the lineup. On Saturday against Texas Tech, he made his biggest impact yet with nine tackles, a tackle for loss and a pass deflection. When healthy, Long has the potential to be West Virginia's top defensive player. -- Trotter

24. LSU: WR D.J. Chark

Chark is the Tigers' top receiver and has also been a threat in the return game. As quarterback Danny Etling's main target, and with the ability to change field position in a second in the return game, he has a chance to be the Tigers' most important utility guy down the stretch.

25. Memphis: Rushing defense

If the Tigers are going to make a serious run in the American -- and push for a New Year's Six bid -- the rush defense needs to get better. Memphis has allowed 242 yards per game on the ground (not counting sacks), which ranks 114th nationally. The Tigers struggled against UCLA's woeful ground attack, allowed three rushing TDs to a bad UConn offense, and watched UCF run for 350 yards in a Week 5 loss. In fact, the only team to rush for less than 150 yards (not including sacks) against Memphis was FCS school Southern Illinois. -- Hale