Finally, Flozell Adams broke the silence with a few angry words punctuated by an anguished shriek.

What the massive offensive tackle uttered was unintelligible, but in many ways, it communicated exactly what many onlookers outside the visitors' locker had to be thinking:

How could this have happened?

Entering the fourth quarter with a seemingly insurmountable 10-point advantage and an inspired, suffocating defense, the upset-minded Cowboys (8-5) unraveled in stunning fashion to drop a 20-13 decision Sunday to the Pittsburgh Steelers (10-3).

The gut-wrenching loss ended Dallas' three-game winning streak and may force it to win out to make the playoffs.

"We just gift-wrapped it for them at the end," Patrick Crayton said.

The heartbreaker - perhaps the most painful of the Tony Romo era - left even the most confident players wondering if they have what it takes to rebound next week at home against the New York Giants, who won the division with the Dallas loss and will be playing to secure the NFC's No. 1 seed.

With Atlanta (8-5) losing to New Orleans, the Cowboys tentatively are in the playoffs as the second wild-card entry based on a better conference record than the Falcons (6-4 to 5-4).

But Dallas is also now 17-29 in December since 1996. And it's hard to imagine the Cowboys winning out against the Giants, Baltimore and Philadelphia after they folded against the Steelers.

"We just have to go out and play," Terrell Owens said. "I have no answers."

The Steelers scored 17 unanswered points in the final 7:15, with the winning score coming on Deshea Townsend's 25-yard interception return with 1:40 left, warming a crowd of 60,594 on a day when it was 22 degrees at kickoff.

"We're losing. Game over," Bradie James said when asked what he was thinking when Townsend stepped in front of a Romo pass intended for Jason Witten.

In the end, Dallas simply couldn't overcome Romo's horrendous outing. He made a magnificent play to escape pressure and throw a 12-yard TD pass to Owens, but he also committed four turnovers, three of them interceptions.

"This one's on me," said Romo, who completed 19 of 36 passes for 210 yards after posting back-to-back 300-yard games.

Romo said he was at fault for Townsend's interception.

"I threw it where he wasn't, so that's on me," Romo said.

But Witten insisted repeatedly he was the blame for Townsend's winning play.

"It's completely on me," Witten said. "It shouldn't be on Tony him at all. Tony trusted me, and I slipped. He put it right where he was supposed to."

Townsend said Steelers defensive coordinator Dick LeBeau had the secondary positioned perfectly in zone coverage to defend the play.

"It was a route they had been running all night," Townsend said.

The Steelers scored their only two TDs 24 seconds apart in overcoming a defense that had stopped it on a fourth-and-goal play at the Dallas 1 early in the fourth.

Pittsburgh rallied to make it 13-13 on Ben Roethlisberger's 6-yard pass to Heath Miller with 2:04 left.

Dallas' special teams also played a role in the collapse, allowing Santonio Holmes to return a punt 35 yards to the Cowboys' 25 midway through the fourth. Four plays later, Jeff Reed kicked a 41-yard field goal to make it 13-6 with 7:15 left.

"That hurt us just as bad as the turnovers did," Dallas coach Wade Phillips said.

The loss wasted an eye-opening performance by Tashard Choice. Dallas turned to the rookie after deciding to leave Marion Barber (toe) at home, and Choice responded with 88 rushing yards on 23 carries, the most the Steelers' top-ranked defense has surrendered this season, and five catches for 78 yards.

"It don't even mean nothing," Choice said. "It means something as far as the coaches understanding what I can do, but all I care about is winning. I could have had a terrible game, and if we won, I would have had a smile on my face. But when you lose it, takes it all out of you."