PITTSBURGH — Pittsburgh Steelers defensive end Aaron Smith has a right shoulder injury that coach Mike Tomlin said “potentially could be significant.”

Smith, injured Sunday in Detroit, was being evaluated Tuesday. The Steelers are not yet certain how long one of their most reliable and productive players will be out, although they apparently are anticipating an extended absence.
Smith’s agent, Peter Schaffer, told The Associated Press in an e-mail that he was awaiting a doctor’s report.
“Aaron is in great spirits and is looking forward to being healthy and playing this year,” Schaffer said. However, he did not say if that meant Smith might not return until the postseason.
Smith has been with the Steelers (3-2) longer than any player except wide receiver Hines Ward and defensive back Deshea Townsend. He is one of the keys to their 3-4 alignment and is often cited by teammates as being the most underrated player on what was the NFL’s top defense the last two seasons.
Smith has 13 tackles and two sacks in five games and blocked a field goal attempt during the Steelers’ 13-10 victory over Tennessee on Sept. 10. He also is one of the Steelers’ primary run stoppers.
Tomlin said first-round draft pick Ziggy Hood is not yet ready to replace Smith, and that Travis Kirschke, Nick Eason and Hood would be used in his place.
“He’s got a lot of talent,” Tomlin said of Hood, the former Missouri player. “He’s not out of the oven yet, if you will. We acknowledge that. He acknowledged that. And as long as we continue to do that, he’ll move in the right direction. ... But by no means is Ziggy Hood a potential replacement for Aaron Smith at this point.”
The 33-year-old Smith sat out the last four games of the 2007 season because of a torn biceps muscle.
Steelers safety Troy Polamalu, who has missed four games due to a torn left knee ligament, and running back Willie Parker (left big toe) are expected to return Sunday against the Cleveland Browns (1-4). Parker has missed two games.