Mark Clayton, Ike Taylor

Ravens wide receiver Mark Clayton (right) can't hang on to the ball as he takes a hit from the Steelers' Ike Taylor in the first quarter of the AFC championship game. (Baltimore Sun photo by Doug Kapustin / January 18, 2009)

The Ravens' improbable Super Bowl run ended with an uncharacteristic performance by Joe Flacco.

Finally looking like a rookie quarterback in the playoffs, Flacco made critical mistakes that cost the Ravens in a 23-14 loss to the Pittsburgh Steelers in yesterday's AFC championship game.

The sixth-seeded Ravens (13-6) rebounded from a 5-11 season because of the big arm and poise of Flacco. But they couldn't return to the Super Bowl in Tampa, Fla., because of him.

With a windchill of 15 degrees at Heinz Field, the NFL's top-ranked defense turned Joe Cool into Joe Cold.

Pressured throughout the game, Flacco completed 43.3percent of his passes (13 of 30) for 141 yards, tying a career worst with three interceptions (after not throwing an interception in his first 49 playoff passes). His quarterback rating of 18.2 was his lowest in 19 NFL games.

Adding injury to insult, Ravens running back Willis McGahee had to be stabilized and carted off the field after a violent hit by Steelers safety Ryan Clark in the final four minutes.

McGahee took a short pass from Flacco, turned to go upfield and ducked just as he was about to be hit by Clark. He fumbled on the hit, and the ball was recovered by the Steelers.

McGahee had movement in his arms and legs but had significant neck pain, according to a report from the Ravens' locker room. The team later said McGahee is "neurologically intact," but would be spending the night in a Pittsburgh hospital.

"We'll move on," Flacco said. "But we're a little disappointed at this point."

Behind 16-14 in the fourth quarter, Flacco had a chance to win the game. Instead, the normally calm quarterback lost it.

Staring down his favorite wide receiver Derrick Mason, Flacco was intercepted by Troy Polamalu, who returned it 40 yards for a touchdown.

That sealed the Ravens' eighth loss in their past nine trips to Heinz and propelled the second-seeded Steelers (14-4) to the Super Bowl, where they will play the Arizona Cardinals.

"I think Troy was able to read my eyes," Flacco said. "He was able to jump over there and make a play. I didn't see him over there until I was on the ground."

The mistake epitomized the rockiest game for Flacco, who had become the first rookie quarterback to win two playoff games.

The consensus was that this loss was a setback but would not derail Flacco, whose play revitalized an organization that has long searched for a franchise quarterback.

"I'm not going to sit here and say Joe played a certain way," first-year Ravens coach John Harbaugh said. "Joe went out there and competed, battled, fought and tried to find a way to win a football game. I don't have any complaints about that."

The Ravens' defense, which had thrived on takeaways during the regular season and playoffs, caused only one yesterday - a fumble forced by Ray Lewis.

Still, the NFL's second-ranked defense had only one major blunder, allowing a 65-yard touchdown pass from Ben Roethlisberger to Santonio Holmes. For the rest of the game, the Ravens limited the Steelers' offense to three field goals (34, 42 and 46 yards).

The real problem was a long-standing one for the Ravens - an inconsistent offense - which resurfaced in the team's first championship game since January2001.