(Landover, MD)  --  The Vikings say running back Adrian Peterson suffered a tear to the A-C-L of his left knee in yesterday's 33-26 win over Washington.  Head coach Leslie Frazier is expected to give more details Monday afternoon.  Peterson was hurt on the first play from scrimmage in the third quarter on a helmet-to-knee hit by Redskins safety DeJon Gomes and was carted off the field.  Quarterback Christian Ponder also left in the third quarter after suffering a concussion.  Joe Webb came in and threw two touchdown passes to help Minnesota win its third game of the year.  Toby Gerhart, who replaced Peterson, rushed for 109 yards on 11 carries.