Quarterback Byron Leftwich hobbles off the field after injuring his knee in the Steelers' 19-3 win over the Carolina Panthers Thursday at Heinz Field in the preseason finale.

PITTSBURGH — All of a sudden, losing Ben Roethlisberger for at least a month isn't the Steelers' only quarterback worry. Byron Leftwich, expected to be the fill-in starter, is injured and looks to be out indefinitely.

Leftwich, tuning up for his anticipated Sept. 12 start against Atlanta, sprained his left knee in the second quarter as Pittsburgh beat the starter-less Carolina Panthers 19-3 Thursday night.

Coach Mike Tomlin said Leftwich would undergo an MRI today, but the quarterback's teammates sounded discouraged. Backup Charlie Batch called it a "serious" injury, and Dennis Dixon — now the likely starter — said he couldn't talk to Leftwich because doctors were working on the knee so intensely.

"It's an opportunity, I guess, but it's unfortunate for Byron for what he went through. But this team has to continue to go forward," said Dixon, who has started only one NFL game. "I know once he's going to come back he's going to give us nothing but tremendous support."

As Dixon talked to reporters, Roethlisberger — leaving the Steelers' locker room for the last time in at least a month — leaned close and offered words of encouragement. Roethlisberger will meet Friday with NFL commissioner Roger Goodell to learn if his suspension for off-field behavior will be reduced to four games, as expected, or stay at six games.

"It's very tough, kind of emotional," said Roethlisberger, who cannot practice with the Steelers while suspended. "I've just got to go do what I've got to do."

Carolina coach John Fox knew what he had to do to avoid injury in a meaningless game, and that's rest his starters. Not only did starting quarterback Matt Moore not play, backup Jimmy Clausen also didn't get off the bench, and with predictable results.Leftwich (4 of 6, 39 yards) was hurt on an 18-yard completion to Emmanuel Sanders as running back Mewelde Moore and safety Marcus Hudson collided near him with 10:25 remaining in the first half. Leftwich immediately clutched his knee in pain.Leftwich was examined by team doctors on a stretcher behind the Steelers' bench, then limped into a nearby tunnel that leads to the locker room. As Leftwich was being helped off, Tomlin immediately lifted Dixon, who completed his only pass for a 23-yard touchdown to rookie Emmanuel Sanders.While Carolina's starters never saw the field, most of Pittsburgh's regulars played into the second quarter, and there were starters on the field when Leftwich was hurt.Batch, the longtime backup who looked to be in danger of not making the roster, played the final 2Z\x quarters and handed off on nearly every play. Batch attempted only four passes.Jeff Reed accounted for most of the scoring with field goals of 33, 43, 31 and 32 yards.Despite opposing Carolina backups, Pittsburgh's starters went three-and-out and Roethlisberger was knocked off his feet twice during the opening series. Roethlisberger completed passes of 16 yards to Arnaz Battle and 13 to Heath Miller on the second drive before spending the rest of the game wearing a ballcap turned backward and a towel around his neck.With Heinz Field barely half filled on a 93-degree evening — though the announced crowd was 52,130 — there was no reaction when Roethlisberger led the offense onto the field. Just as during training camp, where Roethlisberger was warmly received, fans appear to be focusing on the upcoming season rather than the quarterback's off-field behavior.Asked if it will be tough watching on TV, Roethlisberger said, "Absolutely."

Linebacker Patrick Bailey brings down Carolina's Josh Vaughan Thursday in the Steelers' 19-3 preseason win.