Pittsburgh Steelers' team doctors believe quarterback Ben Roethlisberger could miss three weeks because of rib and shoulder injuries, ESPN.com reported Sunday. Roethlisberger will not play Sunday night's game against the Baltimore Ravens. The team hopes he can return by Dec. 2 for its rematch against the Ravens, therefore missing only two games. However, a source familiar with the situation told ESPN that it is not likely. Roethlisberger has said his rib injury threatened his aorta, but a source said team doctors believe the surrounding arteries, vessels and soft tissue are more affected. Since there is no treatment or procedure available to repair Roethlisberger's rare injury, it has to heal itself. Roethlisberger was injured last Monday against the Kansas City Chiefs. Byron Leftwich will start in his place.