Tomlin cited Dwyer's consistency as the reason he officially has been named the starter. The coach said Dwyer also is the Steelers' healthiest running back at the position.
"He's been consistently the most productive guy. I think we have a large enough body of work to be able to identify that at this point," Tomlin said. "Obviously, we've been working at less than ideal circumstances with the rotation and the shuffling of those guys due to health and lack of production. But over the course of the last several weeks, it's obvious that he is healthy and he is the most productive of the group."
Tomlin also said Tuesday that quarterback Ben Roethlisberger, who has missed the past two games with shoulder and rib injuries, threw the ball Monday, and the team will "leave the door open" for him to play.
Roethlisberger has a 50-50 chance of playing Sunday against the Ravens, a team source told ESPN.
The Steelers have dropped both games Roethlisberger has missed, including a 13-10 loss to the Ravens in Pittsburgh two weeks ago. Byron Leftwich started in that game, but missed Sunday's 20-14 loss to the Cleveland Browns with a rib injury. Charlie Batch started against the Browns and threw three costly interceptions.
Tomlin said Batch would get snaps with the first-team offense early in the week.
At 6-5, the Steelers trail the first-place Ravens (9-2) by three games.
Longtime starter Rashard Mendenhall fumbled twice against the Browns, losing the ball once. Dwyer and fellow running backs Chris Rainey and Isaac Redman also lost fumbles. In all, the Steelers turned the ball over eight times.
Tomlin on Tuesday said that turnovers were "unacceptable."
Dwyer leads the Steelers in rushing with 429 yards in eight games. The Steelers have used a rotation at the position this season in large part because of the health of Mendenhall, who had offseason surgery on his ACL and injured his Achilles after he returned.
Polamalu has played just five quarters all season after injuring the calf in the opener at Denver and aggravating the injury Oct. 7 against the Eagles. Brown has missed the past three games after injuring his ankle in a victory Nov. 4 over the New York Giants.
Brown's return will be welcomed as Mike Wallace, a Pro Bowler a year ago, is struggling. He had just one catch against the Browns and couldn't hold onto a pass that turned into one of Batch's three interceptions.
Tomlin allowed Wallace is struggling and there's a possible demotion in the works. Wallace has started 41 of Pittsburgh's last 43 games, but the team listed as either Wallace or Emmanuel Sanders as the starter alongside Brown in the depth chart released Tuesday.
"Mike is frustrated and rightfully so," Tomlin said. "He's not producing like we'd like him to and he'd like to."
First-round draft choice David DeCastro, meanwhile, is looking good to make his NFL debut against the Ravens. The offensive guard suffered a knee injury in the preseason and was activated Monday.
ESPN NFL Insider Ed Werder, ESPN.com AFC North blogger Jamison Hensley and The Associated Press contributed to this report.