Adrian Peterson practices again

Adrian Peterson was feeling good Thursday after his first two practices since his September knee surgery "went pretty smoothly." But it is still unlikely that he will suit up for the Vikings on Sunday against the Indianapolis Colts.

Peterson said he is still targeting a return to the lineup for the Christmas Eve game against the Green Bay Packers. But neither he nor coach Mike Zimmer has definitively said that the running back won't suit up on Sunday.

Zimmer said Thursday morning that deciding whether Peterson will be activated from injured reserve (and if so, when) is not completely up to Peterson.

"It's a combination when we sit down and talk with the medical people," the coach said before practice. "It's a lot to do with the medical."

Zimmer added that other factors will come into play as both the player and the team decide if and when Peterson will return to the lineup.

"We'll have to see where he is at with his conditioning. There's so many things to figure out," he said. "I think he's in pretty good shape, but he hasn't sat in meetings for three months. There's a lot of things to consider."

A few hours later, Peterson acknowledged that the decision is not his alone.

Peterson, who had surgery to repair a torn meniscus in his right knee on Sept. 22, plans to keep wearing the titanium knee brace he strapped on for the past two practices, though he admits it is "a little uncomfortable."

Peterson was asked about his statement last week that he would not play again this season if the Vikings were eliminated from playoff contention.

He responded by reminding everyone that he was rushing back from a major injury and acknowledging that he has to consider his long-term health.

"The injury is a four- to six-month injury," the 31-year-old running back said. "In my mind, I'm telling myself that it's 100 percent healed. But I really won't know until I look and see it in images [from medical testing]. With that, you've got to be smart about how you approach everything going ahead."

He added: "I'm extremely hungry to get out there and help these guys win."

Defensive end Justin Trattou missed practice after injuring his forehead in a fluky collision with wideout Adam Thielen after Wednesday's practice.

There was positive news, though, regarding center Joe Berger, who has missed two games with a concussion he suffered on Nov. 24. He has now suited up for back-to-back practices, albeit on a limited basis, giving hope he could start Sunday. Nick Easton has had ups and downs in his place.

"The hardest [offensive line] position in my opinion when you have to change a guy out is center because he's the guy that directs everything," offensive coordinator Pat Shurmur said. "That's the toughest position."

Quarterback Sam Bradford (shoulder) was limited for a second straight day.

When Mike Priefer got his first job coaching special teams at the NFL level in 2002, Adam Vinatieri, then with the New England Patriots, already was in his seventh season. Another 14 years later, Vinatieri is still going strong.

"He's one of the best. He's, in my mind, a Hall of Famer," Priefer said. "I do appreciate a guy like him because he's been so consistent."