Tight end Dennis Pitta had concussion effects that knocked him out of Sunday's game in Pittsburgh, according to Head Coach John Harbaugh.
Pitta suffered the injury on the Ravens' first offensive drive. He caught a 5-yard pass short of a first down and was hit hard by Steelers safety Ryan Clark and linebacker Lawrence Timmons.
Pitta, who leads the team's tight ends with 38 catches for 381 yards and three touchdowns, was slow to head to the sideline and was taken to the locker room for immediate evaluation.
He was also examined for a concussion last week during the game against the Oakland Raiders. He later returned to action, showing he had not suffered an injury.
Veteran backup Billy Bajema stepped in for Pitta in Pittsburgh opposite of Ed Dickson. Bajema was called for a holding penalty in the second quarter on what would've been a 7-yard run from running back Ray Rice.
Ravens cornerback Chris Johnson, who was signed Tuesday and thrust into action, suffered a hamstring injury. It came in the first quarter after he caused a key fumble from wide receiver Mike Wallace.
That left the Ravens' secondary depleted considering Lardarius Webb (knee) and Jimmy Smith (sports hernia) are also out. It was down to Cary Williams, Corey Graham, Chykie Brown and safety Anthony Levine, who was pulled up from the practice squad.
"[Secondary Coach] Terryl Austin deserves a lot of credit," Harbaugh said. "He's done a great job with that group with the injuries."
Defensive tackle Haloti Ngata (shoulder) played throughout the game and said he felt better after not playing last week.
"I just had to get a feel, kind of testing out my shoulder each play," Ngata said. "It just got more comfortable and better and better."
Injuries mounted on both sides. Pittsburgh quarterback Byron Leftwich hurt his shoulder on his first-quarter touchdown run and later had his ribs evaluated. Steelers running back Isaac Redman suffered a concussion and was ruled out.