Defensive end Aaron Smith, who sustained a torn rotator cuff injury against the Detroit Lions, has been placed on the injured reserve list, ending his season.
To replace Smith on the 53-man roster, the Steelers have signed rookie defensive end Ra'Shon "Sonny" Harris, their sixth-round draft choice who was cut in September. Harris has been on the Carolina Panthers practice squad.
Coach Mike Tomlin said Smith's injury will force the Steelers to use a committee of players to replace him, including veterans Travis Kirschke and Nick Eason and No. 1 draft choice Ziggy Hood.
Smith is one of the most underrated defensive ends in the league because his specialty is playing the run, not sacking the quarterback. The last time the Steelers played without Smith, 33, for an extended period, their rush defense all but collapsed.
That was in December 2007, when Smith tore a bicep in a game against the New England Patriots and missed the final three regular season games and a playoff game against the Jacksonville Jaguars. The Steelers had the league's No. 2 ranked rush defense at the time.
In those four games without Smith, the Steelers allowed 629 yards rushing, an average of 157.2 yards per game.