According to J.P. Peterson of WQYK-AM 1010 (h/t JoeBucsFan), Legarrette Blount will miss several weeks with a Grade II MCL tear. This sounds severe, but it is the same thing as a Grade 2 sprain. It basically means that the MCL has been partially torn, which requires several weeks of rest to repair but generally can be treated without surgery. This was the injury that prevented Jay Cutler from finishing the NFC Championship Game last season.
How long Legarrette Blount will remain out depends on the severity of the sprain. Looking at the history of MCL sprains in the NFL, there is an outside chance that he could be back against the Chicago Bears next week. Rick Stroud says that Blount will miss 1-2 games, which seems about right. Blount had looked very good so far this season and was a pivotal part of a re-vitalized rushing attack. With Josh Freeman struggling the Bucs want to rely on their running game, but this will be tough without their feature back.
With Legarrette Blount out, 31-year old running back Earnest Graham has been named the starter. Graham has run for 84 yards on 18 carries this season, mostly as a third-down back. He was the main starter for most of 2007 and 2008, accumulating 1,461 yards in those two seasons.
Rookie RB Allen Bradford and fourth-year player Kregg Lumpkin could also be called upon to share the load. Bradford and Lumpkin are both big backs who should be able to power through some tacklers, but neither have shown much so far this year or in the preseason.
UPDATE: Scratch that, the Bucs waived Allen Bradford. They now have two healthy running backs on the roster: Earnest Graham and Kregg Lumpkin. Okay then.