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.
NFL Media Insider Ian Rapoport reports that tests on Lewis' knee were inclusive and he will have an MRI on Monday. Rapoport adds there is no swelling or pain but the ACL felt loose, according to a source informed of Lewis' 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.