Star running back. In his prime. Tears his ACL in his fifth NFL season. At the age of 26.

It's no wonder Adrian Peterson's knee injury hits home with former Denver Broncos star Terrell Davis, who experienced a similar setback in 1999.

Like Peterson, Davis attacked rehab. Yet he was never the same, playing just 13 games while rushing for 983 yards and two touchdowns after the injury.

So Davis cautions those who see Peterson's progress and expect him to be a Pro Bowl player again soon, offering two areas to monitor when Peterson returns.

For starters, Davis believed his knee injury made him think too much.

"Rather than being instinctive, you start to choreograph your moves," Davis said in a recent ESPN interview. "As a running back, you just can't choreograph your moves. You have to work off instincts."

Davis also points out it wasn't his injured right knee that bothered him most after he returned. It was his left knee that forced his 2002 retirement, the meniscus and cartilage deteriorating as he compensated for his injury.

"By that time, I had favored my other knee so much that [my left knee] started to wear out on me," Davis said.