Video (00:52) : After Adrian Peterson was spotted working out at Vikings practice, head coach Mike Zimmer inevitably faced questions about his return

Adrian Peterson has taken another step in his recovery from knee surgery.

The star running back, who had surgery to repair a torn meniscus in late September, was spotted running short sprints while his Vikings teammates practiced at Winter Park this morning. Head athletic trainer Eric Sugarman watched closely before the two walked inside toward the locker room.

Tuesday was not the first day Peterson had resumed running, according to head coach Mike Zimmer. Asked when Peterson was healthy enough to start running again, Zimmer said “I don’t know, I’m not in charge of the rehab.

“He’s doing good. He’s doing good,” Zimmer added. “He’s probably ahead of schedule, I guess. I don’t know.”

Since Peterson was hurt during the Week 2 win against the Packers and underwent knee surgery on Sept. 22, the Vikings had been holding out hope that the reigning NFL rushing champion could return in December. There are now five games left for the Vikings, who have lost five out of six.

Peterson’s return is still not imminent, because he has yet to return to practice. Peterson, 31, can officially be activated from injured reserve at any time.

Asked how Peterson could boost the Vikings’ 32nd-ranked running game, Zimmer declined to look ahead of Thursday night’s game against the NFC-leading Dallas Cowboys (10-1).

“I don’t know, we’ll worry about all that when that happens,” Zimmer said. “Right now, we have to focus on Dallas.”

In other Vikings injury news, safety Harrison Smith and cornerback Captain Munnerlyn returned to practice Tuesday and wide receiver Stefon Diggs and middle linebacker Eric Kendricks participated for a second straight day.

Both Smith and Munnerlyn were officially limited in their returns to practice.

Quarterback Sam Bradford was limited again Tuesday due to an ankle injury.

Outside linebacker Chad Greenway was also back in the house after being excused yesterday with his wife set to give birth to their fourth child.

Not practicing for the Vikings were center Joe Berger (concussion), cornerback Marcus Sherels (ribs) and defensive tackle Sharrif Floyd (knee). Those three likely won’t suit up for the Vikings on Thursday night.