According to two sources with direct knowledge of Patriots linebacker Jerod Mayo's injury, Mayo sprained the medial collateral ligament in his right knee on Monday night against the Buffalo Bills.

One source said that Mayo was expected to be out 6 to 8 weeks with the Grade 3 MCL sprain, but the other source said that the timetable is "not that bad" and Mayo is expected to be back quicker than that.

Mayo suffered the injury following a 16-yard run by Buffalo running back Fred Jackson during the first quarter of the Patriots' 25-24 win over the Bills. That was only the sixth defensive play of the game for the Patriots, excluding plays nullified by penalties.

The second-year linebacker and 2008 NFL Defensive Rookie of the Year was able to walk off the field under his own power and was examined on the sidelines before heading back to the locker room. He did not return.

Today Patriots coach Bill Belichick said the injury to Mayo, one of the team's two defensive captains, along with Vince Wilfork, and its defensive playcaller, was not considered season-ending.

"I don't think that is what it is," said Belichick.

Now, we know.