NORMAN, Okla. -- Oklahoma cornerback Aaron Colvin confesses things don't quite feel the same this spring.
Tony Jefferson is no longer flanking him at safety.
Kenny Stills isn't there fighting with him to get open.
And Landry Jones isn't around to try and throw passes over his head.
"I can't lie, a lot of guys have left," Colvin said. "Landry, a bunch of receivers, the defense we lost a lot of guys.
"It is kind of a different feel on the field."
Colvin isn't lying. The Sooners have lost quite a bit of star power off last year's team.
Jefferson, a three-year starter, led Oklahoma last season with 119 tackles -- 34 more than any other Sooner defender.
Stills, who once set Oklahoma freshman-receiving records, spearheaded the Sooners' passing attack with 82 receptions, 959 receiving yards and 11 touchdowns -- all team-highs.
Jones, finally, finished his college career in Norman breaking almost every one of the school's quarterbacking records -- including games started.
Together, the three formed the nucleus of a team that held national championship aspirations until Oklahoma's Oct. 27 home loss to Notre Dame.
But after the season, Jefferson and Stills announced they were going pro, joining Jones and a host of other key outgoing Sooners like left tackle Lane Johnson, cornerback Demontre Hurst and safety Javon Harris; leaving Oklahoma with much to replace.
The biggest challenge -- and dominant storyline of the spring -- will be how Oklahoma succeeds Jones, who has been quarterbacking the Sooners since 2009.
Blake Bell, who has spent the last two seasons pounding the ball out of the short-yardage "Belldozer" package, entered the spring as the favorite over Kendal Thompson and Trevor Knight. Bell, a rising junior, has more experience on the field and operating the offense in practice as Jones' backup last year.
Coach Bob Stoops, however, has indicated he won't name a starter until the fall, which will give Thompson and Knight plenty of opportunity to make a move in the competition.
"It'll be interesting just to see what all happens with that whole deal," Jones said recently. "I'd give the edge to Blake just because he's been in the system longer. But those two other guys coming up, they're just as talented."
The left-handed Thompson, son of former Barry Switzer wishbone quarterback Charles Thompson, has made rapid improvement with his throwing mechanics over his two years on campus, and already boasted the quickest feet of the three.
Knight, meanwhile, dazzled as Oklahoma's scout-team quarterback last fall, then dazzled in the weight room with his strength and speed over the winter.
So far, Bell has been solid. But Thompson and Knight have already made enough plays in team drills to suggest the derby might go down to the wire.
"They've all played well at times, and all made mistakes as well," offensive coordinator and quarterbacks coach Josh Heupel said this week. "Nobody has differentiated themselves yet."
Whoever differentiates himself and wins the job will still have plenty of weapons to work with, including receiver Jalen Saunders who seemingly is primed to take over for Stills as Oklahoma's go-to receiver.
Saunders, cleared to play by the NCAA in October after transferring in from Fresno State over the summer, instantly won a starting job and sparked the Sooners' passing game. He caught 15 passes against Notre Dame, then against Oklahoma State totaled 162 receiving yards and returned a fourth-quarter punt for a touchdown to spur Oklahoma's comeback victory.
Even with the uncertainty at quarterback, the Sooners face many more questions on the other side of the ball. Off a defense that struggled to stop anyone at times in 2012, Oklahoma brings back just four starters, and two of those -- defensive lineman Chuka Ndulue and Gabe Lynn -- have been moved to different positions.
Lynn, who played nickelback last season and cornerback the year before that, is now at free safety in place of Jefferson. Lynn might not possess Jefferson's tackling ability, but coordinator Mike Stoops is banking that Lynn will make up for that by covering plenty of ground defending the pass.
"Gabe is making a conscious effort to prove to everybody that he can be a quality safety in this league," Colvin said. "I've got all the confidence in him."
As for star power, the Sooners might still have enough lingering around to be a surprise team in 2013.
As Texas found out during his 95-yard touchdown run, running back Damien Williams is capable of scoring from anywhere on the field, when healthy.
Trey Millard, who averaged six yards per carry and 11.2 per catch last year, has been one of the best playmaking fullbacks in the nation.
And in Colvin, a first-team All-Big 12 selection in 2012, the Sooners have one of the best returning cover men in college football.
"I am trying to be one of the best there is," Colvin said. "And push myself and this team to another level."