NORMAN, Okla. -- Oklahoma's spring practices begin Saturday, March 5, and coach Bob Stoops already sees improvements from his starting quarterback.

Junior quarterback Baker Mayfield was in contention for the Heisman Trophy in 2015, but ahead of next season, Mayfield has made a concerted effort to get in better shape.

"He’s already improved his body," Stoops said at his Thursday press conference. "I was teasing him just the other day and I said ‘Baker, you’ve improved your body.’ He’s leaned up, gained strength and quickness but he’s eliminated some body fat. He’s stronger and hasn’t lost weight."

Mayfield isn't only trying to improve himself, however.

Oklahoma's only other option at quarterback appears to be early enrollee Austin Kendall, and Mayfield has taken the freshman under his wing.

Kendall enrolled in January, and while the coaches haven't been able to teach him yet, Mayfield's backup is already making strides at preparing for his first season with Oklahoma.

"This is a big time. They've already been over there working once or twice a day on either their routes or going through their passing schemes and reads," Stoops said. "He's already experiencing our offense, and we haven't even been able to have a chance to coach him yet.

"I know Baker's done a great job of mentoring him and coaching him and getting him started. But now we'll have a chance to make a big jump out of here in the spring with Lincoln [Riley] getting with him and spending more time with him."

Stoops says Kendall doesn't appear to be behind physically. He mentioned the freshman is sneaky quick, and he fits in well with OU's group.

Stoops addressed Cody Thomas' situation as well. The redshirt sophomore opted to re-join the baseball team soon after OU's Orange Bowl loss and the coaches aren't planning for Thomas to return in the fall.

Thomas would be welcomed back, Stoops said. But OU's staff feels they'll be comfortable with their quarterback session at the end of their summer session once they can get Mayfield and Kendall on the field.