ARLINGTON, Texas - Troy Polamalu whiffed on a tackle. James Harrison was nearly invisible.

Not the way the Pittsburgh Steelers drew this one up.

Pittsburgh's big-play, hard-hitting defensive leaders were nowhere to be found when the Steelers needed them most as Aaron Rodgers and Green Bay's offense led the Packers to a 31-25 victory Sunday night.

"It's incredibly humbling," Polamalu said. "Toughest loss I've ever had in my life."

Harrison stood in front of his locker, his head down and his voice barely above a whisper.

"I don't feel anything but pain," he said.

And that from a guy who's used to dishing it out.

"I just feel frustration, anger," Harrison said. "We just lost a Super Bowl. How the hell do you think I feel?"

He let the fans know, going on Twitter shortly after the game and typing out one simple word: "Sorry."

That pretty much summed things up for the Steelers defense, which isn't used to having to explain how they couldn't get the job done.

"They were hitting the big plays downfield," linebacker LaMarr Woodley said. "We let them out of third-down situations. When you let a team like that out of third-down situations, you lose the game like we did tonight."

The Packers were 6 for 13 on third down, including a 29-yard touchdown catch by Jordy Nelson that put Green Bay up 7-0.

"We weren't able to get any turnovers on defense," said Polamalu. "That was the difference."

Polamalu was the NFL Defensive Player of the Year, but was anything but the impact player who helped get the Steelers to this point. He had a chance to make a big play early, but delivered only a glancing blow on James Starks.

Polamalu delivered his biggest hit the very next play - as Greg Jennings caught a 21-yard touchdown pass.

"I had some opportunities to make some plays," Polamalu said. "I was just off a step here or there."

Harrison had a sack, but made most of his noise with his mouth during the week while criticizing the NFL. He didn't have much to say after this performance, though.

"I mean, everybody is probably going through a little bit of, 'If I had done this, or what if I had done that?'" Harrison said. "I guess everything happens for a reason. I don't know what that one is right now."

Dick LeBeau's defense was one of the strengths all season for the Steelers, who have a long legacy of punishers - The Steel Curtain among them - who helped bring six previous titles to Pittsburgh. This team expected to do the same, with Polamalu and Harrison leading the way, as they so often have during the last few seasons.

But Polamalu finished with three not-so-memorable tackles, while Harrison had only the sack of Rodgers in the third quarter and a few quarterback hits.

"We had the opportunity to go out there and make the right plays," Polamalu said, "but we didn't."

It wasn't just Polamalu and Harrison to blame, of course. The Steelers' suspect secondary gave up several big plays as the Packers, even without the injured Donald Driver for most of the game, took aim at Bryant McFadden, William Gay and the rest of Pittsburgh's defensive backs.

"We don't grade on a curve," coach Mike Tomlin said. "We're not interested in moral victories and things of that nature. We didn't play well enough to win and Green Bay does, and we tip our hat to them because of that."