EDEN PRAIRIE, Minn. (AP) — Minnesota Vikings running back Adrian Peterson is moving forward in the recovery from surgery on his right knee.

Peterson was seen running some short sprints in the team's indoor facility on Tuesday, while the athletic training staff supervised and his teammates went through practice on the field. With five games remaining in the regular season, there's no timetable for Peterson's return, but the four-time All-Pro pick could be ready sometime in December.

Coach Mike Zimmer has consistently refused to entertain any speculation about whether the Vikings might have the franchise's all-time leading rusher in the backfield again this year, but when pressed on the topic by reporters he acknowledged that Peterson was "probably ahead of schedule" in his rehabilitation. Zimmer said the running session, which took place during the portion of practice that was open to the media, was not the first for Peterson.

"He looked good to me," cornerback Captain Munnerlyn said. "I'm just amazed at the things that he can do. Other people with that injury, it might take them four to six months, but this guy he's ready to roll. I think he'll be back, and he's definitely going to help this team."

Peterson previously beat expectations to recover from surgery to repair a torn ACL and MCL in his left knee and joined the Vikings for the 2012 season opener. He went on to rush for 2,097 yards that year and win the NFL MVP award.

The Vikings (6-5) are last in the NFL in rushing with 71.1 yards per game and 2.8 yards per attempt, with particular trouble in short-yardage situations that haunted them in a few of their losses. Even behind an injury-ravaged offensive line that has struggled to open holes all season, adding Peterson to the anemic attack wouldn't hurt. His presence, at least, would be a morale boost for a team desperately trying to stop a slide after a 5-0 start.

"We'll worry about all that when that happens," Zimmer said. "Right now, we have to focus on Dallas."

The Vikings host the league-leading Cowboys (10-1) on Thursday.

Peterson rushed for a paltry 50 yards on 31 carries in two games before tearing his meniscus against Green Bay on Sept. 18 and had surgery four days later. If he were to return for the game against Indianapolis on Dec. 18, that would be a little less than three months from the operation. The rematch with the Packers on the road is on Dec. 24, the five-year anniversary of the ACL and MCL injury to his left knee.

Peterson's teammates were predictably excited, speaking with more certainty than hope.

"He looked good, and it kind of caught me off guard," left guard Alex Boone said. "We were doing a little walkthrough, and he was running around. We look forward to his return."

Munnerlyn and safety Harrison Smith, both dealing with ankle injuries, returned to practice on a limited basis on Tuesday. So did linebacker Chad Greenway after the birth of his daughter. Linebacker Eric Kendricks (hip), wide receiver Stefon Diggs (knee), quarterback Sam Bradford (ankle) and defensive end Everson Griffen (shoulder) were limited participants but should also be good to go for Thursday. Center Joe Berger (concussion) and punt returner Marcus Sherels (ribs) are the two key players likely to miss the game.

___

For more NFL coverage: http://www.pro32.ap.org and http://www.twitter.com/AP_NFL