DALLAS - In the bedlam of the jubilant Giants’ locker room 20 minutes after the game had ended, Antonio Pierce could still feel his heart pounding like a drumbeat.

They might have even heard it in Green Bay.

“I’m speechless,” the Giants linebacker said in the wake of New York’s stunning 21-17 upset of the Dallas Cowboys on Sunday. “My heartbeat is normally between 48 and 52 and it’s about 150 right now. I don’t even know what to say.”

That's not normal for the loquacious Giants defender, but this wasn’t a normal day in the NFL playoffs. The Giants had just knocked off the No. 1 seed in the NFC ... at their own playground ... after losing to the same twice during the regular season.

This was about the Giants’ defense holding Tony Romo and the vaunted Cowboys’ offense to three second-half points. This was about two incredible defensive stops on the Giants’ side of the 50-yard line in the waning moments.

This was a gut check. And the Giants not only survived, they thrived.

“No one picked us,” Pierce said. “No one expected us to hold a team that has scored about 80 points on us this season to 17.

“So we are heading to Green Bay ... I couldn’t think of anything better.”

This was as much about the Giants’ perseverance as it was a Cowboys’ failure.

“I think everyone saw our character out there,” Pierce said. “I think everyone knows what the New York Giants bring now. If you aren’t a believer now, please don’t become one. Stay exactly how you’ve been the whole season and don’t change.”

Offensively, the Giants did just enough to win.

Quarterback Eli Manning did what coach Tom Coughlin had asked of him. He managed the game, completing 12-of-18 passes for 163 yards and two touchdowns.

The Giants scored on their opening possession when Manning hit Amani Toomer with a 52-yard touchdown pass, but the Cowboys, stitching together impressive drives of 96 and 90 yards, led 14-7 just before halftime. That’s when the Giants delivered a stunning blow that changed the game.

With just 47 seconds left until intermission and the ball at their own 29, Manning marched the Giants 71 yards in 7 quick plays, hitting Toomer over the middle from four yards out for the game-tying score.

“We knew we weren’t going to take a knee,” Manning said. “We had pretty good field position and two timeouts left. We were going to try and give it a shot.

“It was big. They had all the momentum with that long drive. Our defense was gassed. They were just out on the field for so long. We didn’t have a lot going our way and to get a touchdown on that drive was a big momentum builder.”

It certainly seemed to inspire the Giants’ defense, which gave Romo fits in the second half. After being dominated by the Cowboys’ offensive line for 10 quarters, the Giants’ defenders responded in the final 30 minutes.

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“They were the toughest team we faced this year, besides New England,” Romo said

And remember, the Cowboys beat the Packers, too.

Romo was just 18-of-36 for 201 yards and one touchdown, a five-yard fade to Terrell Owens, and was never able to establish a vertical passing game. His longest completion of the game was for 20 yards.

“We didn’t make big mistakes,” said Giants’ defensive end Justin Tuck. “We didn’t give them a big play.”

Trailing 21-17 after Brandon Jacobs’ one-yard plunge capped a short 37-yard, 6-play Giants’ drive early in the fourth quarter, The Cowboys had two near-picture-perfect opportunities to take the lead back in the final seven minutes.

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A defensive holding penalty gave Romo and the Cowboys a first down at the Giants’ 47. The Cowboys killed themselves with penalties. An illegal formation penalty wiped out a 20-yard completion to tight end Jason Witten and Romo was flagged for intentional grounding when he tried to throw a pass away.

The Cowboys’ final shot started at the Giants’ 48 and an 18-yard completion to Witten put them at the 22 with 31 seconds to play and no timeouts left.

It came down to fourth-and-11 from the 23 and Romo’s deep pass over the middle for Terry Glenn was intercepted in the end zone by R.W. McQuarters.

“In the second half, we hit them in the mouth,” linebacker Kawika Mitchell said.

“That was the first time we actually all played together,” said Osi Umenyiora. “We came out and showed what we’re made of.

“We knew if the score was close in the fourth quarter, we were going to be all right.”

Even better than all right. They just earned a trip to Green Bay.

Let the drumbeat continue.