PITTSBURGH – Right arm tucked into a black sling, weary eyes betraying a decided lack of sleep, Ben Roethlisberger tried to stay positive Wednesday after the worst — and by far the most harrowing — injury of his career.

Roethlisberger, the Pittsburgh Steelers’ quarterback, believes he can return this season despite spraining his right shoulder and suffering what he called a dislocated rib in Monday night’s overtime victory against Kansas City.

He’s just not sure when he’ll be ready. And his medical team appears nowhere close to figuring out how to get him there.

“From what (the doctor) said, he’s trying to talk to experts because there is no case study over the exact same thing,” Roethlisberger said. “We’re just trying to talk to people because we don’t know.”

All Roethlisberger knows for certain is doctors are concerned the rib, which he injured while getting sacked by a pair of Kansas City linebackers in the third quarter, could puncture his aorta if jostled around.

He also knows he’ll be a spectator indefinitely while the surging Steelers (6-3) try to track down AFC North-leading Baltimore (7-2). The rivals meet twice over the next three weeks, with the first showdown coming Sunday night at Heinz Field. Veteran backup Byron Leftwich will take the snaps in Roethlisberger’s place, looking for his first win as a starter in six years.

“I’m not going to go out there and try and be Ben,” Leftwich said. “We see the game differently. He’s physically able to do some things that I can’t do, but that doesn’t mean I can’t go out there and do my job.”

TEXANS: Linebacker Tim Dobbins was fined $30,000 for a helmet-to-helmet hit that gave Chicago quarterback Jay Cutler a concussion.

Dobbins said he plans to appeal.

BILLS: Defensive end Chris Kelsay will miss his second straight game with a neck injury after being ruled out by the team from playing Thursday night against Miami.

Kelsay has been out since getting hurt in practice last week. The team hasn’t revealed the exact nature of the injury.

49ERS: Quarterback Alex Smith went through position work in a non-contact black jersey, his status still unclear for Monday night’s NFC showdown with Chicago after he sustained a concussion Sunday against the Rams.

Coach Jim Harbaugh kept an eye on Smith from several yards as he worked with backup Colin Kaepernick and No. 3 quarterback Scott Tolzien to get reps.

BEARS: Kicker Robbie Gould ripped the surface at Soldier Field, then apologized for it.

Gould blasted the field, saying he might have to think about re-signing with Chicago when his contract expires after next season. He told reporters he hopes to remain with the Bears but isn’t sure he wants “to deal with that as I get older as a kicker.”

JETS: New York signed running back Kahlil Bell, who spent parts of the last four seasons with Chicago.

Bell will add depth to a banged-up backfield with backups Joe McKnight (sprained right ankle) and Bilal Powell (concussion) uncertain to play Sunday against St. Louis.

COWBOYS: Running back DeMarco Murray said there’s “a chance” he could return Sunday against Cleveland after missing four games with a sprained foot.

Murray has been out since rushing for 93 yards in a loss at Baltimore. He had 90 yards in the first half but sustained the injury in the second quarter. He had one carry in the third quarter before coming out for good.

PACKERS: Linebacker Clay Matthews will miss Sunday’s game at Detroit with a hamstring injury.