Sometimes top prospects do not pan out. Expectations are piled onto players who fail to reach the big things promised by their rankings.

Several college football players are creeping up on that final chance to shine. These guys aren't busts yet, but the clock is ticking past the 11th hour.

Some have played key roles for a long time but never produced at the expected level. Others may have seen their production hampered by injuries, or they've been blocked by others on the depth chart. But their paths to playing time are a little clearer in 2021. In several cases, a change of scenery already has occurred.

Then there are those who've simply flopped and need to turn it up a notch.

Can they find the final formula to turn things around? Here are some former top prospects facing now-or-never scenarios.    

Stephen Carr, USC Running Back

USC running back Stephen Carr is a perfect example of a player who has gotten on the field for a lot of important reps.

There's nothing wrong with a college career in which the 6'0", 215-pound runner has played in 34 games, carried the ball 264 times for 1,319 yards (5.0 average) and scored 13 total touchdowns.

But there was so much more expected from the Fontana, California, recruit when he was the nation's No. 20 overall player and third-ranked running back in the 2017 class.

Now, entering his final season in Troy, Carr is once again projected to be a role player in a crowded backfield that includes last year's starter, Vavae Malepeai; Texas transfer Keaontay Ingram; Kenan Christon; and Brandon Campbell.

Carr has rarely been fully healthy during his college career, and if he could go an entire season without having any nagging issues and get ample reps, it's possible he could have a huge campaign that would catapult him into the eyes of scouts and salvage a pedestrian career.

The rising senior has never eclipsed 400 rushing yards in a season, and whether he does this year depends on how big of a role he can carve in offensive coordinator Graham Harrell's game plan.    

Ben Davis, Transfer Inside Linebacker

If you've forgotten about how huge of a prospect Ben Davis was in the 2016 recruiting class, join the masses. When you make barely a whimper in a career that was expected to be shouted from rooftops, people tend to forget.

Granted, it's hard to break into the rotation at Alabama, where head coach Nick Saban signs highly rated recruiting classes every year, but Davis was the nation's 10th-rated player and the top inside linebacker in the country.

At 6'4", 250 pounds, the Gordo, Alabama, product looks the part. Now, he's trying to turn around his career by hitting the transfer portal and playing his final year elsewhere. 

According to Inside Texas, Davis is a good bet to land with head coach Steve Sarkisian and the Longhorns, and the Jack linebacker should be able to rush the passer the way Joseph Ossai did for Tom Herman last year before entering the NFL draft.

In limited action (21 games, mostly on special teams), Davis had seven tackles, including one for a loss and a sack. With the depth chart nowhere near as daunting in Austin, it's time for Davis to carve a niche for himself and a more important role for a good team.

If he can't do it this year, he's out of options.  

Jarrett Guarantano, Washington State Quarterback

Former Tennessee quarterback Jarrett Guarantano started games for the Vols throughout all four seasons from 2017 to '20, flashing a strong arm and moments of brilliance.

But he was also maddeningly inconsistent, playing himself to the sideline with terrible turnovers, timing issues and a lack of pocket presence. He became a lightning rod for criticism in Knoxville.

On the surface, Guarantano's stats look strong: He completed 61.1 percent of his passes for 6,174 yards, 38 touchdowns and 17 interceptions, but he never lived up to the expectations of being the nation's top-ranked dual-threat quarterback in the 2016 class.

Despite quality numbers, there was equal amounts frustration, which leads to plenty of question marks about his NFL viability. That's why it was no surprise when Guarantano elected to use the extra year of eligibility granted by the NCAA because of COVID-19.

He transferred to Washington State, where he could have a terrific rebound season for head coach Nick Rolovich in the run-and-shoot offense. The competition won't be quite as tough as in the SEC, but he might be able to put everything together and get an NFL opportunity after a big finale in the Pac-12.     

Hunter Johnson, Northwestern Quarterback

Northwestern's Hunter Johnson, who has seen his once-promising career take a turn into obscurity, would have loved to have had a career like Guarantano.

After flipping from Tennessee to Clemson and signing with the Tigers as a part of the 2017 recruiting class, the 5-star prospect from Brownsburg, Indiana, was expected to be Dabo Swinney's next great quarterback after the Deshaun Watson era.

It didn't work out that way.

Johnson could never unseat Kelly Bryant, and when Trevor Lawrence came in the next year, Johnson was relegated to an afterthought and transferred to Northwestern. He was dreadful in six games as a Wildcat in 2019 and hasn't worked his way into the lineup since.

Last year, Indiana transfer Peyton Ramsey led Northwestern to a 7-2 record, and with South Carolina transfer Ryan Hilinski expected to win the job in 2021, Johnson again could be on the outside looking in.

Johnson has completed just 52.6 percent of his career passes for 666 yards, three touchdowns and five interceptions. If he can't beat out Hilinski, it's going to be a disappointing career for a player who was so promising as a prospect.          

Jack Jones, Arizona State Cornerback

Jack Jones hasn't done himself any favors throughout a career that has taken him from the USC Trojans (with whom he originally signed) to the Arizona State Sun Devils.

The versatile defensive back was the nation's No. 19 overall player in the 2016 class out of Long Beach Poly High School and figured to be a star. But he was dismissed by USC because of academic struggles.

Then, according to Joey Kaufman of the Orange County Register, Jones was arrested on charges of felony burglary after breaking into a Panda Express in June 2018. A plea deal reduced the charges to a misdemeanor. After Jones went to JUCO, he got another shot at big-time football. His former high school coach, Antonio Pierce, is now the Sun Devils defensive coordinator.

In 2017 at USC, he finished with 40 tackles and four interceptions. In 2019 as a member of the Sun Devils, he had another flashy year with 45 tackles, 13 pass breakups and three interceptions, leading to high hopes for 2020.

But a suspension for team-conduct reasons and the team's COVID-19 issues led to him playing just two games. 

If he can put everything together in his extra year of eligibility, Jones is talented enough to be an all-conference player and head to the NFL.         

Caleb Kelly, Oklahoma Linebacker

Oklahoma linebacker Caleb Kelly is another player with electrifying talent and the ability to have a breakout campaign in 2021.

The defender isn't on a lot of radars after missing all but four games in 2019 and sitting out 2020 because of a knee injury. The last time he was a starter for the Sooners was in 2018, but before that, he was on the verge of being a star.

The No. 24 overall player and third-ranked outside linebacker in the 2016 recruiting class made an impact almost immediately.

Over his first three years, Kelly recorded 153 tackles, including 11 for a loss and five sacks. Now, all of the attention is on players like Nik Bonitto, Isaiah Thomas and Brian Asamoah. But do not sleep on Kelly. 

With his elite ability and experience (24 career starts and 41 games of action), Kelly likely will be entering his sixth season of eligibility with a chip on his shoulder and plenty to prove.

No matter how crowded the linebacking corps is, Kelly is going to get opportunities to shine if he's healthy. 

Tyjon Lindsey, Oregon State Wide Receiver

Despite Tyjon Lindsey's lack of ideal size, recruiting services were high on him in the 2017 recruiting class. 

The nation's No. 50-ranked prospect and seventh overall wide receiver was expected to do huge things at Nebraska after coming out of the famed Bishop Gorman High School. Yes, he was 5'9", 161 pounds, but he was a dynamo with the ball in his hands, and the Cornhuskers didn't have many players with his ability.

Lindsey never put it together for the Big Red, and he wound up at Oregon State. Though he's played two seasons at Nebraska and two with the Beavers, Lindsey has never enjoyed anything above mediocrity.

He has 44 catches for 466 yards and five career touchdowns, and he finished with just 11 grabs for 159 yards and three scores a season ago in six games. Still, that was better production than before, so returning for a fifth year of eligibility could mean big things.

Head coach Jonathan Smith needs a game-breaking threat at receiver for 2021. Maybe this is finally the year for Lindsey to break out. If he doesn't do it now, he'll never match the expectations coming out of his prep powerhouse.     

LaBryan Ray, Alabama Defensive Lineman

No matter how well the majority of the guys on this list do in 2021, becoming a first-round draft pick will be a long shot. That's not the case for Alabama defensive lineman LaBryan Ray.

The 5-star prospect out of Madison, Alabama, was the nation's No. 28-ranked player in the class of 2017 and expected to be yet another star along the defensive front for head coach Nick Saban. Thanks to sitting behind talented players and battling some injuries, it hasn't panned out that way.

But the 6'4" weak-side defensive end has potential to be a consistent anchor on what could be Alabama's strongest unit in 2021. He has 65 career tackles, including 11 tackles for loss and 5.5 sacks.

With others like Tim Smith, Justin Eboigbe, Stephon Wynn Jr., Byron Young, Phidarian Mathis, Braylen Ingraham, Jah-Marien Latham, DJ Dale, Jamil Burroughs in the fold, the Crimson Tide have a deep, strong group. But Ray has one of the highest upsides of any of those players, and he's already a strong run-stopping presence.

If his pass-rushing skills catch up and he can stay healthy, Ray is going to turn a lot of heads and will surge up draft boards.         

Demetris Robertson, Georgia Wide Receiver

When the nation's No. 13-ranked player and the No. 1 receiver in the 2016 recruiting class left SEC country to play for Sonny Dykes' California Bears, it was a big deal.

Since then, Demetris Robertson's career has taken a bunch of twists and turns.

He caught 50 passes for 767 yards and seven touchdowns, making a massive impact as a true freshman. The Savannah native got hurt and played just two games the following year. Robertson headed back home to play for the Georgia Bulldogs in 2018, but the speedster has been inconsistent in Athens.

As a junior in 2019, he caught 30 passes for 333 yards and three touchdowns, but he was MIA for much of 2020, catching 12 passes for 110 yards. Entering his sixth and final season of eligibility, there is still a glimmer hope for a resurgence.

Quarterback JT Daniels lends instant-impact credibility to UGA's passing game, and though head coach Kirby Smart has recruited well on the perimeter, Robertson is a veteran who should understand the offense at this point. He was beaten out by younger receivers a season ago, however, and it may be a sign of things to come.

Last month, Robertson was charged with felony interference with government property and a misdemeanor of theft by taking after he allegedly removed a parking boot. If he's available to play in 2021 and Georgia keeps him on its roster, he'll have one more chance to fix an off-track career.       

Aubrey Solomon, Tennessee Defensive Tackle

Another player who left the South was Leesburg, Georgia, 5-star defensive lineman Aubrey Solomon, one of the jewels of Michigan head coach Jim Harbaugh's 2017 recruiting class.

But Solomon struggled to crack the starting rotation under former coordinator Don Brown, registering 19 tackles during his first two seasons. He transferred to Tennessee following in December 2018, but things haven't gone that well in the SEC either.

He has failed to make much of an impact for a team needing playmaking defensive linemen. At 6'5", 315 pounds, Solomon is a big-bodied defensive tackle who looks like he could be a star, but he was out of shape for a lot of the '20 season.

In two years on Rocky Top, Solomon has 45 tackles, including four tackles for loss and two sacks. With Josh Heupel at the helm and Tim Banks leading the defense, Solomon will have a fresh start under a new coaching staff after the Vols went 3-7 in 2020. 

It would be huge for him and the team if he can live up to his 5-star billing.

All stats courtesy of CFBStats and Sports Reference. Recruiting rankings via 247Sports' composite rankings unless otherwise noted.

Follow Brad Shepard on Twitter, @Brad_Shepard.