But Smith, who had the procedure Monday, won't be placed on injured reserve in case he can return this season. Tomlin said the veteran lineman, who was hurt in the Steelers' game against Miami Sunday, will be sidelined for "an extended number of weeks."
"Aaron is a quality player, a veteran leader for us," the coach said. "If there is hope for his return then, of course, we are going to be hopeful for as long as we possibly can."
Smith has 15 tackles in six games this season. He played in five games in 2009 before a shoulder injury ended his season.
He was a fourth-round draft pick out of Northern Colorado in 1999 and was a Pro Bowl pick after the 2004 season.