"The threat is real that Adrian Peterson might never be the same after tearing the anterior cruciate ligament in his left knee Saturday against Washington, deepening the intrigue of a Vikings offseason already rife with tough questions about the direction of the franchise.

But there is enough evidence of post-surgery success among past running backs to encourage Peterson and the Vikings.

Both parties will have to be patient. Peterson, known for his relentless nature that will serve him well through the rehabilitation process, might spend part of 2012 trying to rediscover his explosiveness and confidence. Depending on the speed of his rehabilitation - full recovery can take at least eight months - the Vikings likely will need to ease him into competition, which means more Toby Gerhart next season.

After building the franchise around Peterson, who signed a $96 million extension in September ($36 million guaranteed), the Vikings might need to make a few tweaks to an offense that has appeared passe at times as a run-heavy team in a pass-first league.

Surely, the Vikings have heard the cautionary tales of elite tailbacks whose careers were derailed by this injury.

Denver's Terrell Davis never recorded a 1,000-yard season after a tear in 1999, his fifth year in the league.

While still in his late 20s, Jamal Anderson managed one more season as Atlanta's starter after his 1999 tear. "