The mistakes began with an improbable fumble by Ray Rice early in the second half.
The Ravens then committed two more turnovers in the third quarter, each one giving the ball to Pittsburgh within striking distance of the end zone.
It was all too much to take for Baltimore linebacker Ray Lewis and his proud, overworked defence.
"I've said it time and time again: The No. 1 thing you cannot do is turn the ball over," Lewis said in the stoic Baltimore locker-room. "That will never change in this business. Ever."
Bidding to reach the AFC championship game for the second time in three years, the Ravens had their hopes crushed in a 31-24 defeat Saturday. After bolting to a 21-7 halftime lead, Baltimore's season ended under the weight of an assortment of miscues that included dropped passes, untimely penalties and, most of all, turnovers.
In the third quarter the Ravens allowed Pittsburgh to start three drives inside the Baltimore 26.
"When you play the way we did in the first half and then you go into the second half and as soon as you start the game you give the ball away, it's too much of a momentum swing," Lewis said. "They're already at home, they've already got things going their way, and you turn the ball over three, four times in our end of the field? We're good, but to overcome all of that is harsh on my defence. I wouldn't put that on my defence because we played our hearts out today."
It was the third time in three tries Baltimore has lost a playoff game in Pittsburgh, but this one was different than the rest.
The Ravens led by 14 points when Rice lost his grip on the football — the most surprising miscue in the dreadful third quarter.
Rice had carried the ball 331 times and caught 73 passes this season without fumbling when he slipped out of the backfield to catch a pass from Joe Flacco. Hit in the middle of the field bysafety Ryan Clark, Rice lost the ball.
"I'm not sure who hit it out or whatever. But that's totally my fault. I can take that," Rice said. "I'm not a fumbler, but in a situation like that I've got to be more careful. I was just trying to make a play."
The Steelers scored to make it 21-14, which started a run of 17 straight points.
"They made some big plays and got back into the game score-wise and momentum-wise," said centre Matt Birk, whose early snap on a second-down play led to a fumble by Flacco.
The Ravens managed to tie it on a field goal with 3:54 left, but that only delayed the seemingly inevitable conclusion.
Ben Roethlisberger completed a 58-yard pass to Antonio Brown on a third-and-19 in the closing minutes when the Ravens opted to go with a three-man rush. That play put the ball at the Baltimore four-yard line.
After Pittsburgh scored a touchdown to make it 31-24, T.J. Houshmandzadeh dropped a fourth-down pass from Flacco, ending the season for Baltimore (13-5).
"When the game was on the line, I want my number to be called and it was. And I didn't catch it," Houshmandzadeh said. "That's the moral of the story, the outcome of the game."
Despite getting off to a slow start, the Ravens scored 21 consecutive points to take a 14-point lead at halftime.
Then Rice fumbled. That got the crowd back in the game, and after Pittsburgh scored, the volume increased after Flacco was sacked on first down.
It got worse. Much worse.
After an exchange of punts, Clark intercepted Flacco and took it to the Baltimore 25. That set up an eight-yard touchdown pass from Roethlisberger to Hines Ward, tying the game at 21.
The Ravens went the entire third quarter without a first down.
In the fourth quarter, an apparent punt return for a touchdown by Lardarius Webb was called back because of a holding penalty on Marcus Smith.
Minutes later, Anquan Boldin dropped a pass in the end zone. So instead of taking a 28-24 lead, Baltimore had to settle for a field goal and a tie.
It typified the entire second half.
"It's a shock when it's over," tackle Marshal Yanda said. "It hits you like a sledgehammer."
At the outset, it appeared this game was going to be different — and not in a good way — for the Ravens. Baltimore allowed only one touchdown in each of its previous two games, but Pittsburgh went the distance on its opening possession to take a 7-0 lead.
With the aid of a 37-yard pass interference penalty against Josh Wilson, who protested the call, the Steelers covered 80 yards in surprisingly easy fashion.
And then, just as quickly, things started going Baltimore's way.
Until the third quarter.
"That's a veteran team over there, and we didn't put them away," said linebacker Terrell Suggs, who had three sacks. "We've got nobody to blame but ourselves. They didn't make those mistakes, so they get to go home and play in the AFC championship game and contend for a Super Bowl. We go to the couch."