The Buffalo Bills placed running back Fred Jackson on injured reserve Tuesday.
An MCL sprain will force Jackson to miss the last three games of the season, one derailed from the start.
The 31-year-old Jackson suffered a knee injury in the opener and missed the next two games, then sat out a Week 11 contest against Miami because of a concussion. His latest injury occurred during Sunday's game against St. Louis.
Jackson, who missed the final six games last year with a fractured leg, finishes the 2012 campaign with 437 yards and three touchdowns on 115 carries. He also caught 34 passes for 217 yards and one score.
The Bills filled Jackson's roster spot by promoting defensive tackle Jay Ross from the practice squad.