Adrian Peterson has said that Robert Griffin III is not guaranteed the same speed of recovery from a major knee surgery that the Minnesota Vikings running back achieved last year.

Peterson almost broke the single-season rushing record in 2012, eight months after undergoing a re-build of the anterior cruciate ligament in his right knee.

The Washington Redskins quarterback needed surgery to his ACL and lateral collateral ligament after sustaining a knee injury during the playoffs earlier this month.

Peterson told NFL.com: "Everybody's body heals differently. That's something nobody is going to understand.

"This is also a matter of genetics. Look at my dad. And my mom's side, my aunts and uncles, they're all ripped. At 50 years old, they've got six packs and eight packs.

"My body just heals differently. I know it has a lot to do with rehabilitation and work ethic, but I really credit my genetics for my recovery as much as anything else."

RG3's surgeon has said that he expects the quarterback to be ready for the start of the 2013 season.