Big Ben has suffered his fourth concussion since the 2006 season but it will not keep him out of Sunday's game.

Roethlisberger will play against the Baltimore Ravens as long as he continues to pass post-concussion tests, coach Mike Tomlin said Tuesday. The tests measure a player's memory and reflexes, among other factors, before and after he has been injured.

"He felt normal. He felt fine," Tomlin said of Roethlisberger's first round of testing. "The battery of tests that he took showed that he had no symptoms. We'll continue to monitor his condition and where he is on a day-to-day basis and let that guide our decision-making."

Roethlisberger's condition was caused by a blow to the head when he inadvertently struck the knee of the Chiefs' Derrick Johnson. The injury marked the third time Roethlisberger has received a concussion during a game.

"It could be characterized as a mild concussion, but I hesitate to use the word mild because concussions are not anything to be taken mildly," Tomlin said. "We're proceeding with caution. ... If any symptoms re-occur, or he feels less than fine, we're going to act appropriately."

The Steelers will be dependant on Roethlisberger to stay healthy since backup QB Charlie Batch is out with a broken wrist. He sustained the injury after replacing Roethlisberger in Sunday's overtime loss to the Kansas City Chiefs. Charlie will have surgery this week and he is expected to be inactive for two to four weeks.

Dennis Dixon will be promoted to 2nd string and would be forced into action if Roethlisberger cannot finish the game in Baltimore. Dixon has only thrown only one pass in an NFL game.

"I've been very pleased with Dennis' progress as a third quarterback," Tomlin said. "That's different, of course, than playing against the Baltimore Ravens on national TV. No question we would have to do some things to help him if he plays in this game."

The Steelers are already playing without several key starters. Troy Polamalu and defensive end Aaron Smith remain on the injured list. Starting guard Chris Kemoeatu is also expected to be out for a few weeks. He also suffered an injury in Sunday's game. He will be replaced by rookie Ramon Foster.

Polamalu has missed five games and he played only a few plays in the 18-12 loss to division leading Cincinnati. The Steelers lost four of the games in which Polamalu did not play.

The last time Roethlisberger played after a concussion turned out to be one of his worst performances. He passed for four interceptions in a 41-28 overtime loss to the Falcons in 2006.

The Ravens will most likely blitz the Steelers on a continual basis due to Roethlisberger's vulnerability. If the Steelers offensive line does not protect him we could see a debut for the inexperienced Dixon at QB. Dixon would however add a new problem for Baltimore's defense due to his scrambling ability and foot speed.