Aaron Smith out for extended period

Pittsburgh Steelers starting defensive end Aaron Smith had triceps surgery and will miss an extended period of time, but the team has not ruled him out for the remainder of the season, according to coach Mike Tomlin.

"It was partially torn and it was fixed," Tomlin said of Smith's triceps injury during Tuesday's news conference. "He's going to be out for an extended period of time, and at this juncture we're going to wait that out. Aaron's a quality player, a veteran leader for us, and if there's hope that he will return, then of course we're going to be hopeful as long as we possibly can. That's our mentality as we sit here today."

Smith is one of the most consistent yet underrated players with the Steelers (5-1). Pittsburgh has struggled replacing Smith, a prototypical 3-4 defensive end, in the past when he was injured.

Not only is the 6-foot-5, 298-pound Smith difficult to run against, the push he creates in pass-rushing situations -- even while regularly being double-teamed by 300-pound linemen -- opens up room for James Harrison and LaMarr Woodley to get to the quarterback.

What worries the Steelers is this is the 34-year-old Smith's third significant injury in four seasons. He missed the final 11 games of last season with a torn right rotator cuff, and the Steelers lost five of those. He also sat out the final four games in 2007, including a playoff game, and the Steelers lost all but one.

Statistics also show how valuable Smith is. Last season, the Steelers were allowing an average of 71 yards rushing per game until he was hurt. After that, the average climbed to nearly 100 yards per game, even as opponents also threw with more success against a defense that repeatedly failed to hold leads in the fourth quarter.

This season, the Steelers are giving up a league-low average of 63.7 yards rushing per game.

That's why the Steelers are willing to keep a roster spot open, even if it turns out an injury that occurred during the third quarter of a 23-22 victory at Miami on Sunday sidelines him the rest of the season.

Ziggy Hood, a 2009 first-round pick, is expected to replace Smith in the starting lineup.

Tomlin added that starting defensive end Brett Keisel (hamstring) and linebacker Woodley (hamstring) will be limited during the week. But it's possible one or both could play Sunday night against the New Orleans Saints (4-3). The high-profile, prime-time game will match the past two Super Bowl champions.

James Walker covers the AFC North for ESPN.com. Information from The Associated Press was used in this report.