Jojo Doria

The Vikings' worst fears were confirmed after an MRI revealed that running back Adrian Peterson sustained a torn anterior cruciate ligament in his left knee during Minnesota's 33-26 victory over the Washington Redskins at FedEx Field.

A torn ACL will likely sideline Peterson, the Vikings leader and one of the top running backs in the NFL, for some nine months.

The injury could make it difficult for the 26-year-old recipient of four Pro Bowl and All-Pro selections to return for the start of next season.

Peterson, who was playing in just his second game after missing the previous four with a high ankle sprain, left the contest in the third quarter after taking a helmet to the knee from Redskins' safety Delon Gomes on a three-yard run up the middle.

Peterson was writhing in pain after he fell from the collision. He had to be helped off the field.

The Vikings' fortunes seem to get worse as quarterback Christian Ponder suffered a concussion on the next play following a hard hit in the third quarter. Ponder, like Peterson, did not return to the contest.

The key injuries on back-to-back plays to start the second half seem to ignite the Vikings, who were then led on a furious rally by backup signal-caller Joe Webb.

Webb, along with Toby Gerhart, who came in for Peterson, came up huge for the Vikings (3-12), who broke a 10-10 tie at halftime by rattling 13 points in the third period for a 23-20 lead going into the final frame.

Webb threw for 84 yards and two TD passes, while also running for a score. Gerhart rushed for 109 yards on 11 carries for the victors.

Peterson ran for 38 yards and a score before leaving the game. Ponder, who got hurt after being slammed to the turf on a combined sack by London Fletcher and Adam Carriker, finished with 68 yards on 8-of-13 passing.

Percy Harvin had five catches for 65 yards and a score for the Vikings, who halted a six-game losing skid, their worst losing streak since their 1984 campaign.

Rex Grossman completed 26-of-41 passes for 284 yards, two TD and one interception for the Redskins (5-10).

NFL 2011 - Adrian Peterson Suffers Torn ACL in Vikings Costly Win vs Redskins - Week 16