Roethlisberger expressed reservations Friday about playing, and he and the Steelers' medical staff decided Saturday it'd be best if he sat out.
The Steelers will sign quarterback Tyler Palko off the practice squad and release receiver Shaun McDonald. Dennis Dixon will be the starting quarterback and Palko will be the backup, with Roethlisberger considered as the third option.
Dixon, the third-string option before Charlie Batch broke his left wrist when he came in during last Sunday's loss to Kansas City, has appeared in one game in his two NFL seasons, completing one pass.
FoxSports.com first reported Roethlisberger's status.
Roethlisberger, who was having his best season statistically despite the Steelers' erratic play, went through "a normal week" of preparation for the pivotal game at Baltimore and had said he had every intention of playing.
"It's part of the nature of the beast of playing this game. It's a violent, physical contact sport and there's a chance you're going to get hit," Roethlisberger said Thursday. "You guys don't talk about the bruises we have all over our body. 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."
The last time the Steelers and Ravens met, a berth in the Super Bowl was at stake. This time, the matchup could play a big role in which team reaches the postseason.
Pittsburgh (6-4) beat Baltimore (5-5) three times in 2008 en route to its record sixth Super Bowl title, and its 23-14 win in the AFC title game may have been the most bruising encounter of the bunch.
The defensive battle saw each team punt seven times, with the Steelers putting the game out of reach with Troy Polamalu's 40-yard interception return for a touchdown with 4:24 left.
Both teams trail division leader Cincinnati, which is 7-3.
Baltimore failed to score an offensive touchdown for the second straight game last Sunday, falling 17-15 to unbeaten Indianapolis. Pittsburgh's loss last Sunday was much more surprising, blowing a 10-point lead in a 27-24 overtime defeat to a Kansas City team which entered with a 2-7 record.
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The Steelers' second consecutive loss and the Ravens' fourth in six games helped jumble the AFC playoff picture, and has added fuel to this edition of the rivalry.
"You know it's fireworks every time we play these guys, we're excited about preparing for them," Steelers coach Mike Tomlin said. "You know they're a similar team that we remember competing against. They can say similar things that we're saying, that they're a 5-5 team and not happy with where they are."
Ravens quarterback Joe Flacco has gone three straight games without a touchdown pass for the first time in his career after throwing for 256 yards -- 142 to Derrick Mason -- in last week's loss.
Getting untracked against the Steelers' top-ranked defense won't be easy for the Ravens, whose losses have all come against current division leaders.
"These losses have been against teams that are quality football teams," coach John Harbaugh said. "Call them elite football teams in the league, but we aspire to that."
Flacco had one touchdown, five interceptions and a 44.9 completion percentage while getting sacked 10 times in the three losses to Pittsburgh last season.
Ben Roethlisberger of Pittsburgh Steelers likely to play vs. Baltimore Ravens, says coach Mike TomlinKaka eyes El Clasico
