College football shakeup: Six preseason teams no longer in Top 25

After five weeks of the college football season, almost a quarter of the preseason top 25 are long gome from their lofty preseason perches. Clemson is the most obvious struggler off a preseason No. 4 ranking, but the Tigers have plenty of company. Here's who has fallen from the ranks of the mighty and what the problem has been.

4. Clemson

The 1-3 Tigers are one of the unfortunate stories of the early season. A Week 1 loss to LSU, while disappointing, was understandable. Stumbles against Georgia Tech and Syracuse have been progressively harder for Tigers fans to swallow. Preseason Heisman candidate Cade Klubnik has been sluggish, with just 6.7 yards per pass and six touchdowns against four interceptions.

13. South Carolina

The Palmetto State has had issues with underperforming college football. The Gamecocks opened 2-0, but QB LaNorris Sellers was knocked out early in a rough 31-7 loss to Vanderbilt. Carolina played Missouri well on the road before falling 29-20, but more than anything, the schedule has caught up with Carolina. Their next five games are all against teams in the Top 13 in the AP poll, and three are on the road.

15. Florida

After a 55-0 win over FCS Long Island in Week 1, Florida has basically fallen apart. A shocking home loss to South Florida was followed by more predictable defeats to LSU and Miami. But at 1-3, Florida has six of the remaining eight games on the schedule against teams in the top 18 of the current AP poll. DJ Lagway has been awful, with five touchdowns to six interceptions.

16. SMU

An ACC surprise a season ago, the Mustangs are off to a 2-2 start and have struggled defensively. They gave up 48 points to Baylor and 35 to TCU in a pair of early losses. SMU ranks toward the bottom of the ACC in pass defense efficiency and is allowing an FBS-worst 334.5 passing yards per game.

17. Kansas State

The Wildcats have taken a trio of early losses in close games. While the season-opening setback to Iowa State wasn't a big deal, subsequent defeats to Army and Arizona have definitely hurt. One possible key- Kansas State's 33.9% conversion rate on third down attempts is 13th in the Big 12.

25. Boise State

Boise has only a single loss, but for a team barely in the top 25, a 34-7 defeat to USF to open the season is the problem. Boise get a shot at Notre Dame next week, which could jump the Broncos back in the Top 25. Maddux Madsen at QB has been excellent (1,129 yards, 9 TDs) since the awful Week 1 performance.