Norman, Okla. ? It took awhile, but Jonathan Nelson finally discovered the secret to getting on the field for No. 22 Oklahoma: peanut butter-and-jelly sandwiches.

A string of injuries had held Nelson back since he arrived on campus in 2006, but the last hurdle he had to clear before earning playing time was convincing secondary coach Bobby Jack Wright that he had put enough meat on his slight frame to play safety.

That’s where the PB&J came in.

Strength and conditioning coach Jerry Schmidt put Nelson on a diet centered on the sandwiches and protein shakes and, after three years of trying, he finally gained 15 pounds to get in the game.

“I was pounding shakes before and after workouts and Schmitty had me eating about four peanut butter-and-jelly sandwiches before I went to sleep and when I woke up. And Schmitty actually had sandwiches in his refrigerator that I would eat right after a workout,” said Nelson, a junior from Mansfield, Texas.

“I was basically just stuffing myself and not being able to move during the day. But it was actually good weight.”

Nelson had grown frustrated with the weight issue, which combined with injuries to his hamstring, wrist and knee to keep him sidelined for most of his college career. He had played in only six games over the past two seasons as a member of Oklahoma’s special teams units.

He set out to change that this fall, approaching Wright during two-a-days and suggesting that he could work at safety in addition to his normal cornerback position.

“I was like all in coach Wright’s ear telling him that I actually gained weight and he wouldn’t believe me because since I’ve been here, I couldn’t put on a pound,” Nelson said.

It wasn’t that Nelson didn’t try. Former roommate Dominique Franks recalls Nelson’s eating habits from the days that he’d offer to pick him up something to eat when he went out.

“It was McDonald’s, it was Taco Bell, it was Sonic. It was just anything that he could get his hands on,” Franks said. “I think that was probably the reason why he wasn’t able to gain weight. He wasn’t eating home-cooked meals.”

Gerald McCoy, the Sooners’ muscle-bound, 297-pound defensive tackle added: “He eats and eats and eats and he just won’t gain weight. He’ll lose weight before he gains it. He can eat like me, but his metabolism’s crazy. He’ll eat like a fat man, but he just don’t gain weight.”

The key has been that Nelson went from 172 pounds to 187 without losing speed. Franks compared Nelson’s presence to having a third cornerback on the field, instead of a second safety.

“J-Nel’s one of the fastest guys on the team. Once you put a guy like that at safety, the quarterbacks don’t want to throw the ball deep,” Franks said. “When you have that go-getter back there at safety that can go sideline to sideline, it shuts down a lot of deep balls.”

Now that Nelson is getting his fill of creamy peanut butter and jelly — strawberry and grape are his favorites — he has a different focus that’s not entirely in his control.

“That’s probably the No. 1 thing is to just be healthy, to finally be out there and play more than one or two games without getting hurt,” Nelson said. “That’s a big plus for me. I’m just thanking God every day for having me healthy.”

Defensive coordinator Brent Venables credits Nelson for making intuitive plays and being in the right place on plays since making the move to safety after the second game of the season. He also can provide depth at cornerback.

In a win last week at Kansas, he had a career-high nine tackles and broke up a pass as the Sooners (4-3, 2-1 Big 12) limited the production of Dezmon Briscoe and Kerry Meier, the conference’s top receiving tandem.

Oklahoma hosts Big 12 North leader Kansas State (5-3, 3-1) on Saturday.

“He is super athletic and he just won’t let nobody get behind him because he’s so fast, and he’s got an extremely good work ethic,” McCoy said.