The Vikings had two quarterbacks during Thursday's OTA, and that will remain the same Friday. Quarterback Teddy Bridgewater participated at the start of OTAs on Wednesday but left for Los Angeles for the annual NFLPA Rookie Premiere Photo Shoot. He was one of 39 rookies invited to the event.

Without Bridgewater, four of the team's top five draft picks were not at Thursday's open OTA session. Linebacker Anthony Barr, defensive end Scott Crichton and offensive lineman David Yankey can't continue NFL activities until they finish their school finals. Running back Jerick McKinnon, a third-round selection and the only unsigned draft pick for the Vikings, was the only player present among the top five picks.

Running back Adrian Peterson said he briefly spoke to Bridgewater on Wednesday.

"Seems like a smart kid," Peterson said. "Looking in his eyes, you can see he's hungry. He's out there competing for a starting job, and he's going to have to really work hard because Matt Cassel and Christian Ponder, those guys are out there working extremely hard too to get that starting position."

Cassel received the majority, if not all, of the first-team reps at quarterback and Ponder the rest. All three quarterbacks are trying to get acclimated to offensive coordinator's Norv Turner's offense. Cassel said it's the first time he's played in a numbers system for the play calls.

"The first thing I did when I got the playbook I was trying to figure out what exactly does this number mean," Cassel said. "… It's a lot of work in terms of flash cards, writing stuff down and memorization. Once you start to conceptualize it, it becomes easier for you."

Peterson getting it

Peterson compared Turner's offense to performing open heart surgery without a license during the Vikings' minicamp in April.

He feels a little closer to receiving a license a month later.

"I still want to practice on the side; I got to rent a heart or something," Peterson said. "But where I'm at now, the terminology, I'm starting to pick it up even more. It's all about staying in that playbook, understanding the terminology and breaking the play down. It's going well."

Peterson said he's excited about the ability to be used in passing situations more in Turner's offense. Last year Peterson had 29 catches for 171 yards and a touchdown. There's a good chance those numbers increase given Turner's history of using running backs as receivers.

"The whole running back room is just to be more diverse as an offense," Peterson said. "And be more involved in the pass game is something I've been looking forward to for a long time."

Injury report

Offensive lineman Matt Kalil, defensive tackle Linval Joseph, safety Andrew Sendejo, cornerback Josh Robinson and safety Jamarca Sanford were limited during Thursday's OTA session due to injuries.

Vikings coach Mike Zimmer wouldn't disclose Kalil and Joseph's injuries. He said Kalil had a procedure four to five weeks ago and Joseph dealt with something before the team signed him. USA Today reported Kalil had a minor knee surgery. Zimmer said Joseph will be fine and is getting "real close now."

Zimmer said Sendejo had a back procedure that limited his participation. The safety wasn't present during the team's voluntary minicamp last month. Robinson and Sendejo were held out as a precaution. Zimmer said they were nicked up Wednesday.

Etc.

• When asked if opposing teams know what to expect in his second season, receiver Cordarrelle Patterson said, "I still don't think they know what's coming. I still got a lot left in the tank. Each year I hope to get better."

• Linebacker Chad Greenway on learning Zimmer's offense: "I probably haven't studied this much football in six or seven years. It's been a long time. I'm always carrying that iPad and notebook around, trying to learn and ask as many questions as possible. There's a lot of things to learn, a lot of things these coaches know that come up in this scheme that hadn't come up before. They've done a good job presenting it to us, and we're trying to learn and make it right."