The Minnesota Vikings have decided to take the safe route with star running back Adrian Peterson.

The Vikings announced Tuesday that Peterson will sit out the final two preseason games.

Peterson, who had surgery to repair both a torn anterior cruciate ligament and medial collateral ligament in his left knee on December 31, was taken off the physically unable to perform list on Aug. 12.

"It's just a part of the progression," Vikings head coach Leslie Frazier said. "We think he's doing a good job. There are no setbacks, that's not the reason we're doing it. We just feel like more time with him in practice with some of the things we're doing and the progression of getting him ready for the season is the right thing to do."

Initially, Frazier didn't rule Peterson out from playing in the preseason.

"It just felt like there were more things that we want to give to him in practice than we could by trying to get him ready for a game, say for this instance Friday night. There are a few more things that we'd like to be able to do in a controlled setting rather than a game situation," he said.

The Vikings' season opener is Sept. 9 against Jacksonville, but Frazier declined to guarantee that Peterson will be ready to play by then.

"We're going to do some things in practice to see how responds to a hit and then go from there," he said.

Peterson finished 2011 with 970 rushing yards and 12 touchdowns on 208 carries. It was the first time in his career that he didn't eclipse 1,000 yards rushing.