Elite NFL players come back quickly from injuries

"A guy like Adrian is sort of like Hakeem Olajuwon, who I worked with throughout his career in my work with the [Houston] Rockets. If you have a carrot in front of 'Dream,' he always did better. So if he had a challenge, it brought out the very best in his skills. That's what happened with Adrian."

Said Peterson, whose team plays at the Packers on Sunday, in a conference call with Green Bay reporters: "The recovery for me was knowing that I was starting over, pretty much. It made me hungrier than I already was. This off-season, I definitely learned how to take it to a different level."

Paine had Peterson working out alongside, for instance, a 65-year-old patient who had just undergone a knee replacement. There was no special corner for the Vikings star. He was an important client, yes, but also one of many people looking to resume their lives and careers.

Of course, it was hard to ignore Peterson.

"I usually have 10 to 15 NFL guys in the off-season after surgery," Paine said. "I had [Green Bay cornerback] Tramon Williams, [Ravens safety] James Ihedigbo, starters with great physiques, and they'd just look at Adrian and shake their heads. Seeing him, they just say, 'Wow, he's different.'"

Vikings center John Sullivan said he has repeatedly heard how miraculous Peterson's recovery has been, "but I can't say I'm surprised, because I've known Adrian so long. His work ethic is second to none, and he's just blessed with physical gifts that other people don't have."

Minnesota linebacker Chad Greenway knows how difficult it is to bounce back from ACL tears. He has had them in both knees since college. He has also been around long enough to know what Peterson is doing is historic.

"I was telling some of the younger guys that haven't seen him a lot on our team, 'Just remember, you're watching something special here,'" Greenway said. "This isn't a normal athlete. He's a guy that's just a little bit different."