If Keisel is unable to go, the Steelers will revert to another player with plenty of spot-start experience; Ziggy Hood.
Hood started 12 games and all of the playoffs last season when LDE Aaron Smith went down with a triceps injury. Now, he'll switch over to the right side if he replaces Keisel, which, by all accounts, seems imminent.
While any time a team loses a solid player like Keisel (who's off to a great start this season, one year after being named to his first Pro Bowl team), it's not a benefit, but Hood played well last season, showing steady improvement.
The Steelers were looking for Hood to be their primary back-up defensive end in 2011, after letting Nick Eason go in free agency. His athleticism makes him an ideal fit to play on either the left or right side. It's just a question of familiarity. Considering Tomlin's announcement of the severity of Keisel's injury, Hood will likely be up bright and early Wednesday to prepare himself for at least one start - this one at Lucas Oil Stadium on Sunday Night.
Back-ups filling in isn't new, even this early into the 2011 season. Ramon Foster, last year's starting right guard, changed sides this year as well. He replaced Chris Kemoeatu (knee) at left guard in the Steelers 24-0 win over Seattle in Week 2, and performed very well.
CB William Gay also played well, serving as a replacement for the injured Bryant McFadden (hamstring) in Week 2. Kemoeatu's status, along with McFadden and WR Jerricho Cotchery (hamstring), are undetermined as of yet. Tomlin said they will all practice this week, and no one has been ruled out.