Is it too late for Desmond Bishop to overtake Marvin Mitchell for the starting weak-side linebacker position?

That's what the Vikings are trying to determine, which is why defensive coordinator Alan Williams mentioned Bishop as one of the current second-line players who will get some reps with the first unit when the Vikings play their third preseason game at San Francisco on Sunday night.

"You want to see if a guy can execute against good on good," Williams said. "I think that's one thing we'll try to do this week to make sure the guys we're looking at get good on good. Believe me, the 49ers have enough depth in their roster that we're going to get good on good with our first two groups."

Bishop missed all of last season in Green Bay after tearing a hamstring in the preseason. He wasn't signed until late June, meaning he missed all of the offseason training. Then he hurt his groin, which knocked him out for a week of practices and the preseason opener.

His first live action in a year came at Buffalo on Friday. Williams said Bishop played "well," but wasn't exactly glowing in his remarks when asked about Bishop today.

"There were some plays where he played downhill and had some good tackles." Williams said. "And I think if you talk with him, there were also some plays he left out there on the field, which can be expected in the first extensive full action he's had [in a year]. What we're looking for is to see if he can improve on those things that he didn't do so well and correct those and get better."

Musgrave: Preseason action good for Peterson

Asked today if Adrian Peterson's preseason debut will be good for helping the Vikings' run-oriented offense develop some much-needed rhythm on Sunday, offensive coordinator Bill Musgrave said even a league MVP can benefit from some preseason contact.

"I think it's also [good] for Adrian personally so he can exorcise some of his preseason butterflies," Musgrave said. "So it will help for him to get out there and get a feel for the speed of the game before we get to Detroit" for the regular season opener.

It also helps that the Vikings will game plan this week, something teams typically do for the third preseason game.

"We're going to [game plan] about as similar as we can make it [to the regular season]," Musgrave said. "We don't go above and beyond the call of duty in the preseason, but we definitely want the players to get a feel for the in-season routine."