PPITTSBURGH — Steelers quarterback Ben Roethlisberger is expected to miss Sunday night's game at Baltimore because of a concussion.

Persons familiar with Roethlisberger's status spoke to The Associated Press on condition of anonymity on Saturday because the team has not made an announcement.

The development would force Dennis Dixon — who has thrown only one pass in two NFL seasons — to make his first NFL start in a game the Steelers might need to win to make the playoffs.

Roethlisberger practiced all week despite sustaining his fourth concussion since 2006 during a 27-24 overtime loss in Kansas City on Sunday. On Thursday, during his only interview of the week, he said he had been cleared to play, joking he passed "thousands of tests."

Roethlisberger, however, experienced headaches resulting from the concussion — his knee struck the knee of Chiefs linebacker Derrick Johnson as he leaned headfirst during a running play in overtime — and he began debating the wisdom of playing after consulting with the team's medical staff.

The Steelers continued to list Roethlisberger as questionable on Saturday, meaning there is a 50-50 chance he would play — creating the possibility Roethlisberger could decide at game time he is ready to go, if cleared by team physicians. There also is a possibility he would be listed as the third quarterback, allowing him to play in an emergency.

Foxsports.com first reported that Roethlisberger would not play.

Dixon, the former Oregon quarterback who has not played this season, took more snaps than usual in practice Friday — the first sign Roethlisberger's status might change. Coach Mike Tomlin said Tuesday the team expected Roethlisberger to play, and there were no signs Wednesday or Thursday he wouldn't.

If Dixon does start, the Steelers likely would rely mostly on running backs Rashard Mendenhall and Willie Parker and trim the amount of throws Dixon makes. Dixon was an excellent runner in Oregon's spread offense, but the Steelers — like every NFL team — limit their quarterback's running because of the risk of injury.

The Steelers (6-4), losers of their last two and a game behind Cincinnati (7-3) in the AFC North, were so convinced Roethlisberger would play, they did not sign an experienced quarterback even after backup Charlie Batch broke his left wrist a few plays after replacing Roethlisberger on Sunday. Their game plan for the Ravens (5-5) also was built around Roethlisberger playing.

Batch will miss most or all of the rest of the regular season. Tyler Palko, the former Pitt quarterback who didn't sign or practice with the team until Thursday, would be the backup despite going through only two practices.

Dixon's only game action came in a mop-up role against Cleveland in the final game of last season. He would be the most inexperienced Steelers quarterback to be thrown into a starting role since rookie Mike Kruczek replaced the injured Terry Bradshaw in 1976. Kruczek went 6-0 as a starter despite not throwing a single touchdown pass, and ended his five-season NFL career in 1980 without throwing a scoring pass.

Roethlisberger's apparent decision to not play comes in the same week the NFL has taken a heightened stance on protecting players from head injuries. NFL commissioner Roger Goodell sent a memo to teams outlining steps the league is tasking to reduce head impacts.

Roethlisberger also had two concussions in 2006, one in a motorcycle accident, and another last season in that Browns game in which Dixon played.

"It's part of the nature of the beast of playing this game," Roethlisberger said Thursday. "It's a violent, physical contact sport and there's a chance you're going to get hit. You guys don't talk about the bruises we have all over our bodies. If I showed you a bruise on my shoulder and a bruise on my shin, it wouldn't get talked about as much. It's a violent sport we play."