During the third quarter, Batch threw an incomplete pass to running back Isaac Redman while falling to the ground.
Harbaugh made an unsuccessful challenge of the play, looking for a fumble ruling. The original call was upheld, costing the Ravens a timeout.
"Yes, that was not a good decision by me," said Harbaugh, who's now 3-for-5 this season on replay challenges. "That was not a good decision. I just felt like he was lying on his back and winging it, and I thought maybe his arm wasn't going forward when I saw it. Looking back on it, it wasn't a good challenge."
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The Ravens lost their final timeout with 1:46 left in the game when cornerback Chykie Brown was hurt with a minor ankle injury.
Because the injury occurred in the final 2 minutes, the Ravens were charged with their third and final timeout of the game.
It didn't wind up mattering since the Ravens never got the ball back as Steelers kicker Shaun Suisham knocked in a 42-yard game-winning field goal.
"It's nothing serious," Brown said. "I just tweaked my ankle. I think I stepped on somebody's foot."
Leach delivers big block
Ravens rugged All-Pro fullback Vonta Leach doesn't discriminate, punishing defenders large and small with his powerful blocking.
Leach took down a heavyweight Sunday, sending hefty Steelers veteran nose guard Casey Hampton flying with his feet up in the air. Leach upended the 6-foot-1, 325-pounder, catching him by surprise on a 6-yard Ray Rice run in the first half.
"I had a nice shot on him," Leach said. "He thought he would make a play in the backfield, and I came out of nowhere to hit him. I was just doing my job. It was pretty cool. He wasn't expecting a fullback to come block him. We haven't showed it all year."
The 6-foot, 260-pound Leach also caught four passes for 40 yards out of the backfield.
"We just took advantage of what we were doing, closing down runs," Leach said. "They were able to sneak me out of the backfield."
Saw it coming
Graham darted back into coverage to intercept a high sideline pass intended for running back Jonathan Dwyer.
Through scouting reports of the Steelers, Graham knew what was happening right away.
"We saw it on film several times where Brown threw the ball," said Graham after intercepting his second pass of the season against the Steelers and leading the Ravens with a game-high 11 tackles. "It wasn't a surprise for me. When I saw him get the reverse and I seen the running back leaking out, I figured it was a reverse pass. It wasn't a surprise. I just got to make the play."
Defensive end Pernell McPhee played primarily on third downs, playing for the first time in four games.