The rib injury that the Bears originally hoped running back Michael Bush could play through last week has now landed him on season-ending injured reserve.
The Bears, whose only healthy backup last week was 5-foot-8, 190-pound Armando Allen, re-signed Kahlil Bell as their No. 3 running back.
Bush leads the team with 5 rushing touchdowns as the backup to starter Matt Forte, and he has been the favored ball carrier in short-yardage and goalline situations. He ends his season with 411 yards on 114 carries, a 3.6-yard average.
The 6-foot-1, 245-pound Bush originally suffered the injury against the Seattle Seahawks on Dec. 2. He tried to play the following week, but the injury was aggravated on his first and only carry against the Minnesota Vikings.
Bush was active last Sunday against the Green Bay Packers, but he was not used when the Bears had a goalline situation and instead went with Forte, who failed twice to get into the end zone from the Packers' one-yard line.
"He was in uniform but still we were going to use him only if we had to," coach Lovie Smith said. "He still wasn't quite ready to go."
Bell, who was with the Bears from 2009-11 and started three games last season, rushed for 557 yards on 119 carries (4.7-yard average) over the previous three seasons. He was waived during the 2012 preseason but was re-signed Sept. 15 and had 12 carries for 32 yards. He was waived on Oct. 15.