Adrian Peterson, who suffered a major knee injury on the Vikings' first play after halftime Sunday, knew he was in trouble as soon as he was hit.

"It definitely didn't feel good," he said after the game. "I knew initially right when it happened that it was something serious. So I don't know, I'm just anxious to see, find out and then go forth from there."

"Anytime you take a blow to the knee like that, you're concerned about the ACL, MCL," he later added before learning the extent of his injury. "I'm trying to stay as positive as I can."

X-rays taken at the stadium ruled out any broken bones, but an MRI performed later in the evening confirmed he suffered a torn ACL, the team announced Sunday evening. Multiple reports indicate that Peterson also suffered a torn MCL. Vikings coach Leslie Frazier will give an update on the injury during his weekly press conference Monday afternoon.

Peterson recently missed three games due to a high ankle sprain before returning in Week 15. Even though the Vikings were eliminated from playoff contention weeks ago, Peterson said he doesn't regret coming back to play in the last two games.

"No, not at all, I felt like I was healthy enough to go and be productive," he said. "And you guys [saw], in the first half I was being productive. I felt good coming out in the second half, I just had more energy, and I was just ready to really get things going. But unfortunately it was cut short on the first play."

Peterson will eventually need to undergo surgery followed by a lengthy rehabilitation. It's likely that he will not be ready to take the field by the beginning of the 2012 season, and only time will tell if he'll ever regain his trademark explosiveness. Peterson signed a seven-year, $100 million contract, which includes $36 million in guaranteed money, this past September.

For reaction and updates on Peterson's injury status, visit Vikings blog Daily Norseman.