Pittsburgh ? Ben Roethlisberger’s right knee injury apparently isn’t serious, but Pittsburgh Steelers coach Bill Cowher isn’t ready to say if his quarterback will be ready to play Sunday in Green Bay.

Roethlisberger underwent an MRI exam Tuesday, about 12 hours after the Steelers’ 20-19 victory over Baltimore, and was given a preliminary diagnosis of a strained posterior capsule. The injury affects the range of motion of the knee and can be very painful.

“All ligaments are fine, and we’ll get a further update as the week goes on,” Cowher said Tuesday. “There’s nothing serious coming out of the game as we speak. … Hopefully it’s something he can continue to work through, and we’ll rest him when we can and see where he is at the end of the week.”

The Steelers have a short week of practice before their first trip to Green Bay (1-6) in 10 years, but it is unlikely Roethlisberger will attempt to practice today. The Steelers (5-2) normally want a player to practice at least once by Friday to play Sunday.

Cowher did not specify Roethlisberger’s status – either probable, questionable or doubtful – and is not required to do so until today. The team also said there would be no update on the MRI results until then.

Roethlisberger, 18-1 as an NFL regular season starter, injured a knee for the second time in four weeks in a Monday night game as he caught a cleat in the turf while being hit by the Ravens’ Jarret Johnson during the first quarter. Despite limping for several plays after being hit, Roethlisberger stayed in the game and led two touchdown drives and a fourth quarter drive that resulted in Jeff Reed’s decisive 37-yard field goal with 1:36 remaining.

Cowher said the injury clearly affected Roethlisberger’s throwing and mobility, even though the second-year starter went 18-of-30 for 177 yards and two touchdowns to rookie tight end Heath Miller.

“Sure it had some effect and no question he was hurting, but he gutted it out,” Cowher said. “He was hurting. He told me at halftime he was getting it taped up and that ‘I’m going to give it a shot, but if I’m hurting this team, I’m going to take myself out.’ I said, ‘I expect you to do that. Only you know where you’re at with it.’ “

Roethlisberger started the second half by leading a 10-play, 64-yard drive that resulted in his second scoring pass to Miller, an 8-yarder that put the Steelers up 17-10. Pittsburgh didn’t score again until its final 60-yard drive that ended with Reed’s second field goal of the game, and his second game-winner in four games.

Cowher isn’t surprised Roethlisberger remained effective despite the injury. Roethlisberger’s 112.4 passer rating is the best in the league.

“He’s a very poised quarterback and he has a feel for the game,” Cowher said.