Key storyline for every top 25 team

Jalen Hurts has been Alabama's starter for almost the entirety of the last two seasons, but Tagovailoa is the front-runner for the starting job entering 2018 after saving the Crimson Tide in the National Championship Game. He gave the team a spark and looks more capable with his arm than Hurts, though the team's recent conservative offenses still give the more experienced and mobile Hurts a shot.

The Clemson defense could be historically great, especially up front, where the Tigers have four defensive line prospects who could go in the first round of next year's draft. The offense was the team's Achilles' heel at times last season, ranking only 32nd in points scored, and there is a quarterback competition between incumbent Kelly Bryant and top recruit Trevor Lawrence. If either emerges this season, Clemson could earn the No. 1 ranking in short order.

Georgia's explosive running back duo rushed for more than 2,500 yards collectively last season, meaning the rest of the Bulldogs' backs have big shoes to fill. Among the capable replacements are D'Andre Swift, who averaged 7.6 yards per carry, and top recruit Zamir White, who is returning from a torn ACL. The offense is still in good hands with quarterback Jake Fromm after getting a year as a starter under his belt.

The Buckeyes should have an elite defensive line and running game again, but they'll have a new man behind center for the first time in years. Barrett was the unquestioned starter over the last two seasons, and although sometimes inconsistent, he won't be easily replaced. The Buckeyes are likely to turn to sophomore Dwayne Haskins, though the spot still isn't settled.

The Huskies were somewhat disappointing last year after making the College Football Playoff the previous year, and part of their regression was the play of Browning. After throwing for 3,430 yards and 43 touchdowns as a sophomore, he had only 2,719 yards and 19 touchdowns last year. Key losses on offense, namely John Ross, were partly to blame, but the Huskies still need a big year out of Browning to return to prominence.

The Badgers could have one of their most talented teams ever, returning quarterback Alex Hornibrook, star running back Jonathan Taylor and their elite offensive line. Usually, the team's question marks are on offense, but it's the defense that should have fans concerned this year. Wisconsin was the third-best scoring defense in the FBS in 2017 but lost more than half of last year's starters.

Oklahoma's offense was elite during the Mayfield years, peaking last season with 45 points per game and a Heisman Trophy for the new Cleveland rookie. Now that he's departed, the Sooners will turn to Texas A&M transfer and MLB first-round pick Murray to lead the way. A former top recruit, Murray doesn't have nearly the accuracy of Mayfield but certainly has the athleticism. If the Sooners are able to lean on running back Rodney Anderson, they should remain the favorites to win the Big 12.

Head coach Mark Richt's development at his alma mater is going swimmingly, going 19-7 in two seasons and garnering the team's first 10-win season last year since 2003. However, there are signs the Canes had some luck last year, finishing fourth in takeaways and recovering 62 percent of opponents' fumbles. The good luck evened out late in the year with three straight losses, and the defensive line has been depleted. The team has a lot to prove this year to get back to double-digit wins.

While he's been a top recruiter and news-maker since taking over in Ann Arbor four years ago, Harbaugh has yet to turn the Wolverines into a powerhouse program. Part of the struggles has been Harbaugh's inability to find an elite quarterback, with apologies to Jake Rudock. Ole Miss transfer Shea Patterson could finally be the answer, and the Wolverines will be in contention for the national championship if that's the case after returning most of their elite defense.

Barkley was responsible for more than 1,900 yards from scrimmage and two kickoff return touchdowns last season, helping Penn State score more than 41 points per game and finish 11-2 in 2017. Now that he's off to New York, the Nittany Lions will try to find a replacement for his production, and Miles Sanders looks like the man for the job. He's averaged 6.7 yards per carry in his college career but has only seen 56 carries in two seasons.

Stidham is a top Heisman Trophy hopeful and possible first-round pick in next year's NFL Draft, but the Tigers lost key weapons to injury already in wideouts Eli Stove and Will Hastings. The defense should be very good again after allowing only 18.5 points per game last season, but Stidham could be forced to do it all himself after the injuries at wideout and losses of Kerryon Johnson and Kamryn Pettway at running back.

Mark Dantonio's team successfully rebounded from a nightmarish 2016 season due in large part to quarterback Brian Lewerke's development and a top 20 defense. The defense returns most of its starters, but the offense still has room for growth after scoring only 24.5 points per game last season. The Spartans hope to win the Big Ten this season, but Lewerke will need to take another step forward as the team competes with Ohio State, Michigan and Penn State.

The Irish rebounded with a 10-win season in 2017 due in large part to their great running game. Now they'll have to compensate for the losses of first-round offensive linemen Quenton Nelson and Mike McGlinchey, along with running back Josh Adams and No. 1 wideout Equanimeous St. Brown. The huge losses will put pressure on quarterback Brandon Wimbush, who completed less than 50 percent of his passes last season. 

Running back Bryce Love is the early favorite for the Heisman Trophy, but as we've seen in the past, the Cardinal can't be an elite team without solid quarterback play. Costello didn't exactly light it up last season with only 7.5 yards per pass attempt, and he will need to show some level of improvement for Stanford to win the Pac-12.

The Hokies had an elite defense in 2017, allowing less than 15 points per game. That led to a nine-win season, but the team will be hard-pressed to replace Terrell and Tremaine Edmunds, along with both starting corners. The new faces will have to step up quickly.

Kenny Hill is gone, but TCU fans are excited about new starter Shawn Robinson at quarterback. The offense seemed to be missing some of the explosiveness we're used to seeing last year, ranking only 29th in points scored. The athletic Robinson can make things happen with his feet, as he showed when he ran for 84 yards vs. Texas Tech last November, though his passing accuracy is an unknown at this point.

Fitzgerald's 2017 season ended with a nasty dislocated right ankle. While he's expected to be ready for the start of the season, it remains to be seen if he will be at 100 percent after rushing for more than 2,300 yards over the last two seasons. The loss of Dan Mullen is a double blow for the offense, though former Penn State offensive coordinator Joe Moorhead is capable of keeping the team on the right track offensively.

Darnold and Jones II are almost irreplaceable, but the Trojans will try this year. Top recruit J.T. Daniels looks like the front-runner for the quarterback job, though there are likely to be some hiccups for a true freshman who graduated high school a year early. Jones II also rushed for more than 1,500 yards last season, so the Trojans will have to find offense with new faces.

Quarterback Will Grier could be an underrated value pick in the Heisman race after throwing for 3,490 yards and 34 touchdowns in only 11 games last season. He should continue to put up big points in a Big 12 with some poor defenses, but West Virginia's defense has its own share of issues. The Mountaineers allowed 31.5 points per game last season, ranking 90th out of 130 FBS schools, though it seems like there's almost nowhere to go but up.

Quarterback Brett Rypien is looking to cap off a solid college career in his senior season but will have to do so without Wilson, his favorite receiver over the last two seasons. Wilson had 2,640 yards and 18 touchdowns over the last two years. The defense could also have a tough time replacing do-everything linebacker Leighton Vander Esch, who had 141 tackles, four sacks and two interceptions before getting drafted in the first round by Dallas this year.

The Seminoles were a disaster last season, so much so that some fans were relieved when Jimbo Fisher departed. They brought top offensive mind Willie Taggart to address the issues, which started with Deondre Francois' injury early in the year. Francois will return to battle young James Blackman for the starting QB job, and the success at the spot should determine if the Seminoles are capable of rebounding after winning only seven games last season.

The self-proclaimed defending national champions had a magical season, but now that magic will be difficult to re-create following the losses of head coach Scott Frost and standouts Shaquem Griffin, Mike Hughes and Chequan Burkett. Of course, new head coach Josh Heupel has experience developing great offenses at Oklahoma, Utah State and Mizzou, so quarterback McKenzie Milton might not miss a beat.

Herman's offense struggled to meet expectations in his first season, ranking just 53rd in points scored as the Longhorns struggled to find a quarterback. That spot seems finally settled with Sam Ehlinger, though the offensive line and running game also must improve. The team did win three of its last four games, including wins against West Virginia and Missouri, so there is strong momentum heading into 2018.

Florida fans are tired of the quarterback play at this point, with a merry-go-round since Will Grier departed in 2015. Dan Mullen was hired to address that issue for good after developing Dak Prescott and Nick Fitzgerald at Mississippi State, and the former Florida offensive coordinator could have his answer in freshman Emory Jones.

Former head coach Les Miles was run out of Baton Rouge early in the 2016 season, and Ed Orgeron was retained after going 6-2 in relief. Coming off a disappointing 9-4 season, Orgeron likely needs to show better results to accommodate the high expectations. That will be difficult after losing quarterback Danny Etling, running backs Derrius Guice and Darrel Williams, and top wide receiver D.J. Chark. The team's hopes rest on Ohio State transfer Joe Burrow at quarterback.