An SC sprain is an injury to the joint connecting the sternum and the collarbone. Multiple reports have said that Roethlisberger, who was knocked out of the Chiefs' game early in the third quarter, will undergo further tests and is in a considerable amount of pain but he's yet to be ruled out of Sunday's game.
If Roethlisberger cannot go — and he is known for plaything through pain — Tomlin said that Leftwich, who has played in just two regular season games the past three seasons , would be his starter. Another veteran, Charlie Batch, would then back up Leftwich.
Leftwich completed 7 of 14 passes for 73 yards in relief of Roethlisberger on Monday and admitted after the game that he was rusty. Leftwich, 32, hasn't started more than six games in an NFL season since 2005 when he was with the Jacksonville Jaguars.
"I'm not worried about the capabilities of either men if called upon," Tomlin said. "They're proven veteran players. They're capable performers. Whatever offense or personalities we choose to have, more than anything, if he is to play or either is to play, then obviously this week's preparation will be big and having an opportunity to take snaps and prepare will be big."
Tomlin didn't rule out Roethlisberger not practicing this week and playing Sunday, saying, "I have [done that] before." Roethlisberger is a two-time Super Bowl-winning quarterback who was having one of the best seasons of his career before the injury.
The Ravens (7-2) have a one game lead on the Steelers (6-3) for first place in the AFC North. The two teams will play twice over the next three weeks. However, Tomlin said that the scheduling will have no bearing on how the Steelers proceed with their franchise quarterback, who has flourished in new offensive coordinator Todd Haley's offense, throwing for 2,287 yards, 17 touchdowns and four interceptions in nine games.
"I don't care about the opponent," he said. "They're nameless gray faces to me. I'm not going to change our protocol because of who we're playing."
Since 2004, the Steelers are 0-4 against the Ravens in games that Roethlisberger has missed because of either suspension or injury though all four of those games were decided by six points or less. Meanwhile, Roethlisberger is 9-4 against the Ravens in his career.
The quarterback is also hardly the only Steeler who is banged up. Tomlin said that safety Troy Polamalu, who has been out with a calf injury, is doubtful to play Sunday versus the Ravens. Running back Rashard Mendenhall (Achilles), wide receiver Antonio Brown (ankle), offensive tackle Marcus Gilbert (ankle) and safety Ryan Clark (head) are also questionable for the game.
"We just focus on the healthy guys," Tomlin said. "The injuries are what they are. We're not looking to make excuses. Excuses are the tools of the incompetent. I believe we have a competent football team. The ones that are healthy will prepare, will step in the stadium and the level of expectation will be the same."