Last week, we looked at the biggest reasons for optimism for each team in Mark Schlabach's post-spring top 25. This week, it's the other side of the coin. What has each team worried?

The glass-half-empty crowd might look at Ohio State's progress in the passing game this spring and see that the Buckeyes lost three first-round draft picks from their secondary. As is to be expected from an Urban Meyer team, the talent is there to replace them, but it might take some time to settle in. Safeties such as Damon Webb and Erick Smith will have to show they're ready to be the new leaders on the back end. -- Dan Murphy

The Seminoles are in good shape at quarterback with Deondre Francois, but can they protect him? He was a tackling dummy far too often last season, and though Florida State thinks it has some answers on the offensive line, a rash of spring injuries meant a lot of mixing and matching on the line. Perhaps the extra reps for backups and the versatility required across the board will pay dividends in the fall, but for now, the 34 sacks Francois endured last season remain a big red flag. -- David M. Hale

Remember all those explosive plays Alabama gave up during the championship game loss to Clemson? They reared their ugly head again during the spring game, as the secondary was torched for at least five completions of 30 or more yards. -- Alex Scarborough

Three starters from last season's offensive line -- tackles Zach Banner and Chad Wheeler, plus guard Damien Mama -- are now on NFL rosters, which leaves plenty of uncertainty about how well the Trojans will protect quarterback Sam Darnold. There are some intriguing pieces, namely projected left tackle Chuma Edoga, but the starting combination needs to be sorted out. -- Kyle Bonagura

Both starting defensive ends from one of the Big Ten's better pass rushes in 2016 are gone. The Nittany Lions have some options to replace them who are young (Shane Simmons and Shaka Toney) and slightly more seasoned (Torrence Brown and Shareef Miller). Brown is probably best positioned to have a breakout season on the edge of the line, but spring ball didn't end with an entirely clear picture of how that rotation will work. -- Murphy

Are the Cowboys' cornerbacks ready to go to battle in the Big 12? The league features elite talent at wide receiver, and Oklahoma State, after allowing 7.15 yards per pass attempt last season -- ninth in the Big 12 -- shifted top corner Ramon Richards to safety. Make room from Clemson graduate transfer Adrian Baker, but the Pokes remain short on proven players, with senior Darius Curry and sophomores A.J. Green and Madre Harper likely to earn top spots. -- Mitch Sherman

The biggest question mark is without a doubt at quarterback, but slightly less obvious is the lack of a top option at tailback. Clemson struggled to run the ball at times last season with Wayne Gallman, and now it has to find answers from what is looking like a committee approach. Tavien Feaster needs to refine his blocking, C.J. Fuller and Adam Choice need to show more explosiveness, and incoming freshman Travis Etienne remains a mystery until his arrival this summer. -- Hale

The arrival of receivers Marquise Brown and Jeff Badet and the continued emergence of Jeff Mead were positive developments for the Sooners offensively this spring. Still, whether they'll provide QB Baker Mayfield with the firepower he'll need to keep thriving remains a question going into the fall. -- Jake Trotter

The Huskies became the first team in NFL draft history to see three players from one secondary go in the second round, and that leaves an obvious void to fill. Safety Taylor Rapp is a budding star, and the Huskies have brought in several talented players, but it remains to be seen how closely they can replicate the success of last year's group. -- Bonagura

Kevin Steele's defense had a quietly productive season last year. But with Carl Lawson and Montravius Adams gone from the front seven, it remains to be seen who the team's top pass-rushers will be in 2017. Junior college transfer Paul James III had a big spring game and could be one candidate. -- Scarborough

Quarterback Alex Hornibrook proved his toughness during his first season as a starter. But if for some reason he has to miss time in 2017, there isn't a clear leader to step into his spot. Neither redshirt freshman Kare Lyles nor early enrollee Jack Coan was able to get the offense up to full speed in Wisconsin's short spring scrimmage. Coan showed some promise in catching up to Lyles so quickly, but the Badgers will be careful to keep Hornibrook healthy until September and beyond. -- Murphy

LSU's offense looks different, but does it have the quarterback it needs to contend in the SEC West? Danny Etling didn't have a strong showing in LSU's spring game, but none of the guys behind him (Justin McMillan, Lindsey Scott, Lowell Narcisse) has beaten him yet. The competition will roll into preseason training camp and pick up another contender in true freshman Myles Brennan, who arrives this summer, but the Tigers need to find someone who can lead Matt Canada's offense effectively. -- Sam Khan Jr.

Kirby Smart was pretty pleased with the play of his offensive line for most of the spring, but this group had plenty of hiccups in the spring game. The first-team offensive line gave up five "sacks" and looked out of sorts at times in pass protection. Even with three new starters, this line could be more athletic and more cohesive, but that spring game performance left a lot to be desired. -- Edward Aschoff

Michigan's staff did its best to squeeze as many reps as possible into spring ball, but the experience lost with 10 exiting starters on defense is hard to replace in practice. A lack of experience limits the Wolverines' depth in the front seven. More importantly for a team that depends heavily on playing press man coverage, it leaves them with a big question mark at cornerback. There is a lot of talent at that spot that won't be truly tested until the Wolverines face Florida in the season opener. Cornerbacks coach Mike Zordich said he was happy with his guys this spring, but they "still had a ways to go." -- Murphy

Coach Mark Richt means it when he says he has no idea who is going to start at quarterback. Evan Shirreffs and Malik Rosier finished spring as co-No. 1s, but true freshman N'Kosi Perry will get his shot once fall practice begins and will be given every opportunity to win the starting job. -- Andrea Adelson

As quarterback Keller Chryst recovers from a knee injury suffered in the Cardinal's bowl game, it is unclear who will start when the team opens against Rice in Australia on Aug. 26. If he's ready for training camp, Chryst figures to be the starter (though that's no guarantee). If he isn't ready physically, there are two viable options with former starter Ryan Burns (most likely) and redshirt freshman K.J. Costello. -- Bonagura

The Cards made strides on the offensive line this spring, but they will know much more about the unit once four-stars Ronald Rudd, Mekhi Becton and Toryque Bateman arrive and begin participating in fall practice. The Cards signed their best offensive line class ever, and they are hoping to get immediate contributions from some, if not all. -- Adelson

Do the Wildcats have a difference-maker among the linebackers? We know that K-State lost two, Elijah Lee and Charmeachealle Moore. Seniors Trent Tanking and Jayd Kirby and junior Sam Sizelove bring experience, though primarily on special teams. Tanking is perhaps the top candidate to turn into an all-league candidate, though Kansas State ought to provide a chance for juco transfer Da'Quan Patton or sophomore Elijah Sullivan to emerge. -- Sherman

Linebacker remains a work in progress as the Bulls try to find two new starters to pair with two-time all-conference middle linebacker Auggie Sanchez. Nico Sawtelle and Danny Thomas are the only lettermen at the position who return. Safety Malik Dixon put on weight and made the transition to play linebacker as well. -- Adelson

Are there too many -- or too few -- defensive linemen in position to play at WVU? West Virginia had three stalwarts last season. In 2017, it looks like the Mountaineers plan to take the opposite approach, with as many as eight ends and tackles set to man three positions. On one hand, it means they've had several defenders emerge or return from injury. Conversely, there is no proven star among the group. -- Sherman

The Gators will definitely have to figure out their slim situation at linebacker, but the offensive line went from the darlings of spring to overpowered in the spring game. Four starters are back, and word was that this group took mighty steps forward during the 14 practices leading up to the spring game. But once the lights went on, Florida's line shrank and looked more like last season's struggling group. -- Aschoff

Justin Fuente said before spring opened that finding the right supporting cast was more important than finding his QB. After spring, he's still looking. There's little clarity in the backfield, where Travon McMillian's grip on the starting job is tenuous at best, and the Hokies are still mixing and matching at receiver, hoping to replace the production lost with the departures of Isaiah Ford and Bucky Hodges (combined 1,785 yards, 14 TD). -- Hale

From swinging at lockers with a sledgehammer to putting posters in bathrooms, Tom Herman has drastically attempted to change the culture at Texas this offseason. Talent has never been the Longhorns' issue, yet Texas faded down the stretch of Charlie Strong's final season. Will the Longhorns have a different mentality come fall? That will be revealed soon enough. -- Trotter

From 2002 through 2012, the Broncos were a fixture in the AP poll, finishing in the top 20 in nine seasons. In the four seasons since then? Just once. Boise State remains one of the nation's top Group of 5 programs, but in the College Football Playoff era, does it deserve to be in the title conversation? -- Bonagura

For the most part, Wazzu's 2017 should have been considered a success, but because it was bookended by uninspired losses to FCS Eastern Washington and Minnesota, there has been some understandable grumbling about consistency. The Cougars should be a real threat in the Pac-12 North, but it remains to be seen if they can play at a high level early in the season. Five September games in Pullman should help. -- Bonagura