Obviously, it will take up to nine months, a year or even longer before we have any idea how Saturday's gruesome knee injury will affect the career of Vikings running back Adrian Peterson.

He's such a violent runner with a combination of size, speed and quickness that's rarely been seen. Ever. So who knows if he can recapture that style.

The gut feeling here is Peterson will attack his rehab from a torn left ACL with the same energy he goes after defenders. There's also plenty of examples of running backs who have come back.

Peterson needs to look no further than former Viking and Redskin Terry Allen.

Allen, the Vikings' ninth-round draft pick in 1990, already had suffered an ACL injury when he tore the other one during practice in the summer of 1993. 

Yet Allen came back in 1994 and ran for 1,031 yards and. He then went to Washington and posted back-to-back 1,300-yard seasons. He had 1,309 yards and 10 touchdowns in 1995 and career highs for yards (1,353) and touchdowns (21) in 1996.

Also, Allen's last ACL tear was 18 years ago. The surgical procedure is much more advanced today.