The 2021 college football season is well underway, and NFL scouts have their eyes on the top prospects ahead of the 2022 NFL draft. Unlike last year's truncated season because of COVID-19, colleges are playing full schedules again, so NFL teams will have a much better handle on this year's draft class.

Through the first four weeks of the season, several players' draft stocks across the country have either risen or dropped. Let's take a look at who is improving and who is declining early in the season.

Stock Up: Ole Miss QB Matt Corral

Matt Corral had a breakout season in 2020 numberswise, but the Rebels finishing 5-5 on the year didn't exactly put him on the national radar. Ole Miss is undefeated through September, though, and the Rebels quarterback has been playing lights-out.

Ole Miss had a bye week during Week 4, but the QB's numbers speak for themselves. In three games, Corral has thrown for 997 yards, nine touchdowns and zero interceptions. He's completed 68.8 percent of his passes, as well. Corral is a threat on the ground, too—on the season, he's rushed for 158 yards and five touchdowns. Four of those rushing TDs came during Ole Miss' Week 3 game against Tulane. At 6'2", 205 pounds, Corral has the skill set and frame to further the trend of mobile quarterbacks succeeding in the NFL.

The Rebels are first in the nation in total and scoring offense, averaging 653.3 yards and 52.7 points per game. Corral and Ole Miss have a chance to pull off a major upset next week, as the Rebels face No. 1 Alabama in Tuscaloosa on Saturday. Last season, Ole Miss lost 63-48 to Alabama, but Corral finished the game completing 75 percent of his passes for 365 yards and two touchdowns.

If Corral defeats the Tide and plays as he has in the prime-time slot Saturday afternoon, his stock will go even higher.

Stock Down: Oklahoma QB Spencer Rattler

The Sooners are undefeated through the first four weeks of the season, but Spencer Rattler's performance has been up and down with 1,017 yards, eight touchdowns and three interceptions.

One of those interceptions came Saturday against West Virginia. The home crowd in Norman went so far as to boo the quarterback after his second-quarter pick. There was even a chant calling for Rattler's backup, Caleb Williams, to come in.

Rattler's only touchdown of the night came in the first quarter, as both teams struggled to find the end zone. In the second half, the Sooners managed to make three field goals. On the first of those drives, Rattler missed a third-down throw that went incomplete and then failed to convert on a 3rd-and-22 on the second drive. Oklahoma at least hung on to beat the Mountaineers 16-13.

After the game, Rattler was asked by ESPN reporter Holly Rowe about how he handles his home crowd booing him:

Rowe: "I know it's unusual when you hear the crowd boo. How do you process that moving forward and stay positive?"

Rattler: "I don't worry about that at all. I don't listen to 'em—they're not on the field."

If Rattler wants to improve his stock, throwing fewer interceptions and being a bit more consistent would be a good start.

Stock Down: Texas A&M RB Isaiah Spiller

Isaiah Spiller had a 1,000-yard rushing season a year ago and was expected to play a big role in the Aggies offense in 2021. In the first four weeks of the season, however, he hasn't had too many dominant performances.

His two best games have come in blowout wins against New Mexico and Kent State. He had over 100 yards in both but managed to score just one touchdown. He's only had one other touchdown on the season, during the third quarter of Saturday's loss to Arkansas. That touchdown run was a good one—he went 67 yards on the score to pull the Aggies within a touchdown.

It appears as though Spiller's biggest issue is perhaps not getting enough play calls going his way. After the touchdown, the Aggies didn't hand it off to Spiller once for the rest of the game.

Jimbo Fisher was asked about this afterward, per 247Sports' Andrew Hattersley:

"We did it two or three times. We had a couple calls. There were some RPOs that we threw. We had a nice run out of that. ... We had two or three runs and we RPO'd them because they were playing extra guys in the box and we were throwing them out there and had some run. Then we got behind a little bit and hit a couple runs. And then we had clock management when it got going and backed up. So maybe we could have more, but we weren't getting enough surge."

Spiller has had just 52 carries on the season so far, which is not going to help his stock rise.

No Change: Oregon DE Kayvon Thibodeaux

Kayvon Thibodeaux has played in just two games this season, missing the Ducks' games against Ohio State and Stony Brook because of an ankle injury. He returned Saturday against Arizona, and although he didn't record a statistic, just being healthy enough to play was good to see.

Unfortunately, in the second quarter against the Wildcats, Thibodeaux left the game again, appearing to land awkwardly while trying to defend a quarterback scramble. After the game, Oregon head coach Mario Cristobal told reporters the defensive end didn't reaggravate the injury he suffered early in the season:

"I don't think it'll completely feel normal all the time, but there was no reaggravation of an injury. With him, it's been load management and we reached that. So that's why we pulled him out. Whenever we pull a guy out who has some type of nick or an injury or whatnot, we try to always advance them with either some form of—in his case, it was wearing a different set of shoes; some guys might actually do some rehab work on the sideline. Everything right now with him is from a load-management standpoint and not a reaggravation of his ankle."

Thibodeaux is considered one of college football's premier edge-rushers. He had a breakout season as a true freshman in 2019, recording 35 total tackles and nine sacks, including a forced fumble. During the Ducks' shortened, seven-game season last year, he had 42 total tackles and 9.5 for loss. Although he still doesn't appear to be 100 percent healthy, his first two seasons were impressive enough to keep him at the top of most 2022 draft boards.

Stock Down: Florida CB Kaiir Elam

Similar to Kayvon Thibodeaux, Florida cornerback Kaiir Elam has been dealing with an injury early this season. He left last week's game against No. 1 Alabama in the second quarter, suffering an apparent knee injury. The good news, though, is that it wasn't a season-ending one.

The injury still kept Elam out of the game against Tennessee during Week 4, and Florida head coach Dan Mullen said after the game that Elam is probable for next week's game against Kentucky on the road.

"Yeah, so hopefully Kaiir should be back this [week against Kentucky as] well," Mullen said. "He'll be, what do they say, like, probable this week. And talking to him, hoping he's probable for this coming weekend."

Even as a true freshman in 2019, Elam appeared in all 13 games for Florida, making five starts. If he can get and stay healthy this week, he should be in for a big season.

Stock Up: Fresno State QB Jake Haener

Fresno State's Jake Haener has been lighting up pretty much every opposing defense he's faced so far this season. Through five games, he already has thrown for 1,842 yards and 15 touchdowns along with just two interceptions. He leads the nation in total passing yards and is third in yards per game (368.4). He's had just one game where he threw for fewer than 300 yards: during the Week 2 loss at Oregon, and he missed it by just two yards.

The Bulldogs also had an upset 40-37 victory on the road over UCLA, as Haener threw for a season-high 455 yards. He even did so after taking a couple of big shots from UCLA defenders that caused him to be visibly in pain late in the game. Haener stayed in though and led a game-winning drive capped off by a 13-yard touchdown pass.

"Jake knows he's got to get back up because we need him," Fresno State coach Kalen DeBoer told ESPN's Kyle Bonagura. "I'm not saying that in a way where you're taking it for granted. I'm saying it in a way where he just wills himself to do that. That's the toughness he has and the competitiveness."

Haener and the Bulldogs are now 4-1 on the season and are first in the Mountain West Conference. The QB is more of a traditional pocket passer as opposed to the new generation of dual-threat guys, but NFL scouts can't ignore his stats. As long as Haener keeps putting up these kinds of numbers for this Fresno State offense, his stock will continue to rise.

Stock Up: Georgia NT Jordan Davis

Georgia's Jordan Davis could have been the first nose tackle taken in last year's draft, but he decided to return to Georgia for his senior season. It looks like his decision has paid off so far. Through the first four games, Davis already has eight total tackles and 1.5 sacks. The 6'6" 340-pound lineman had two tackles for loss and one sack against Clemson in Week 1.

"He's elite at pocket push," Georgia head coach Kirby Smart said ahead of the Dawgs' season opener against Clemson. "He's elite power, one of the strongest kids I've ever been around. He helps you the way he's able to run games and things because he's just different. There's just nobody quite like him in terms of the volume and the reps."

Davis played in just nine snaps during Saturday's shutout against Vanderbilt—Georgia was up 35-0 after the first quarter. Looking ahead at Georgia's schedule, Davis' team will need him in the weeks ahead. Next week the Dawgs get No. 8 Arkansas at home, and the Razorbacks come into this one averaging 480 yards per game.

The other big games remaining on Georgia's schedule include at Auburn on Oct. 9 and the matchup against No. 10 Florida in Jacksonville on Oct. 30. If Davis and Georgia's defense keeps playing this well, his NFL draft hopes should climb even higher.