The clubhouse leader for comeback player of the year, who stormed onto New England's roster after two years out of football, left Sunday's 27-10 win over the Redskins with a knee injury.
Lewis had four carries for 14 yards and four catches for 39 yards.
The injury occurred midway through the third quarter. Lewis' leg stiffened and he went down awkwardly at the end of the play. Though he was able to walk off the field under his own power, he was almost immediately declared out for the game.
The rushing burden fell squarely on the shoulders of LeGarrette Blount, who was punishing Washington's defense all afternoon. Brandon Bolden was also seeing some time in Lewis' absence. If Lewis is out for Week 10, James White could be activated and at least take over Lewis' pass-catching role. The Patriots play at the Giants in Week 10 in a late afternoon game.