Continued: Birk's replacement taking charge

The Vikings made it clear they had confidence that John Sullivan could take over at center when veteran Matt Birk signed with Baltimore in March. Sullivan is now getting his opportunity, working with the first team during the three-day minicamp.

He has impressed quarterback Sage Rosenfels. "I think Sully's doing a great job," said Rosenfels, who was traded to the Vikings in February. "He was here all offseason, he's done a great job, really taken the bull by the horns at center. He and I are constantly talking. He's one of those guys who loves to talk the game. I think he learned a lot from Matt Birk."

A sixth-round pick out of Notre Dame in 2008, Sullivan not only has to concern himself with the physical responsibilities of taking on nose tackles but also the mental challenge of making the line calls. Offensive coordinator Darrell Bevell said Sullivan is up to the task.

"He was out here last year when Birk was at home [during organized team activities]," Bevell said. "He jumped in and took charge. He's a confident guy. He's a smart guy. So we're getting good calls out of him and good communication."

Tackling an issue

With defensive tackles Kevin and Pat Williams continuing to fight four-game suspensions for violating the NFL's anti-doping policy-- the sides are due in state court Tuesday -- the Vikings know their other tackles must be ready to go.

"We feel good about the guys that are backing them up, but nobody can really replace Kevin and Pat," defensive coordinator Leslie Frazier said. "They're Pro Bowl guys that could eventually end up in the Hall of Fame. But we feel good about the guys that are backing them up. ... They do a good job for us."

The backup tackles include Fred Evans, Letroy Guion and Jimmy Kennedy. Evans started the final three games last season after Pat Williams was injured.

Etc.

• Rookie receiver Percy Harvin is being used on both punt and kickoff returns, something he didn't do at Florida. "He's done a good job. We really haven't done much kickoff return," special teams coordinator Brian Murphy said. "We saw him catch a few earlier and he did that fine. Punt return, he needs some work on so he'll spend a lot of time with [punter] Chris Kluwe. He's a guy that I look forward to seeing develop."

• Running back Adrian Peterson, who wanted to add 7 to 12 pounds this offseason, said he's actually a pound lighter than his listed weight of 217 pounds from last season. "I got my body fat down and I put on 6 pounds of muscle," Peterson said. "Whatever I can stack on top of that from this time to training camp, that's what I'll try to do."

• Right guard Anthony Herrera (shoulder) and guard/tackle Artis Hicks (biceps) have been limited in minicamp, giving Ryan Cook and Brian Daniels a chance to get reps with the first team. Cook also is getting some snaps at right tackle, as is second-round pick Phil Loadholt.

• NFL Films was in town Saturday shooting a video called "All Day with Adrian Peterson." A crew followed Peterson around -- he was wearing a mike during practice -- to chronicle a day in his life. The DVD is set for an Oct. 13 release.

• Owner Zygi Wilf has attended the first two days of minicamp.

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