Those two plays were the most pivotal in the Cowboys' 20-16 victory at Lincoln Financial Field, allowing Dallas to departleave Philadelphia atop the NFC East.

The Cowboys improved to 6-2 halfway through the regular season while the Eagles slipped to 5-3.

With the score tied at 13 and just over 11 minutes remaining in the game, Eagles quarterback Donovan McNabb tried to pick up the few inches needed for a first down by running a sneak.

He was convinced he had those inches, too.

"I felt like half my body was past the marker," McNabb said.

Side judge Rick Patterson disagreed, saying McNabb had come up short of the first-down marker. Eagles coach Andy Reid challenged the decision with a red flag, but referee Walt Coleman, after going under the replay hood on the home team's sideline, ruled that Patterson's spot was correct.

"By the way he spotted the ball, it made me look like I lost a yard," McNabb said. "Again, I felt like I got the first down, but they had the final call and it went against us."

Reid declined to say how he felt about the spot.

"I can't go into the challenges. I can't do that unless you're willing to pay" for a fine from the league, Reid said. "They called them the way they called them."

The secondfailed challenge gave Dallas the football at its own 45-yard line, and four plays later quarterback Tony Romo was faced with a third-and-14 situation at the Eagles' 49-yard line.

Romo got cornerback Sheldon Brown to bite on a pump fake that left receiver Miles Austin open for a 49-yard touchdown. It was Austin's only catch of the evening.

"He ran a double move, and we were in a cover one," Brown said. "Tony pumped, [Austin] ran a slant, I drove the slant, and he got open deep."

Reid's failed challenge was his second of the game, and it left the Eagles without any time-outs. That proved costly at the end of the game.

After David Akers connected on a 52-yard field goal with 4 minutes, 27 seconds remaining in the game to cut the Cowboys' lead to four points, Dallas managed to convert a couple of first downs, and the Eagles watched helplessly as Romo knelt down three times to run out the clock.

Reid said he had opted to kick the field goal on a fourth-and-11 play because he thought there was enough time to get the football back despite being out of time-outs.

"I thought we could hold them with five minutes left," Reid said. "I thought we could get the ball back and win the game. But it didn't work out that way."

Nothing seemed to work the Eagles' way on this night.

Another failed opportunity in a short-yardage situation during the third quarter also proved costly.

Reid lost a challenge and a time-out on a pass from McNabb to rookie running back LeSean McCoy, leaving the team in a fourth-and-inches situation from their own 42-yard line.

"I guess if hindsight is 20-20, I'd probably like to have those [challenges] back," Reid said. "It didn't go as I anticipated it."

The coach opted to go on fourth down, but tackle Jason Peters was flagged for a false start when he flinched slightly.

Dallas' first seven points came courtesy of a short field provided by rookie receiver Jeremy Maclin when he let a McNabb pass slip through his hands. Dallas' first seven points came after safety Gerald Sensabaugh intercepted a pass that went off the hands of Eagles rookie receiver Jeremy Maclin, giving the Cowboys the ball at the Philadelphia 37-yard line.

Romo led the Cowboys on a seven-play touchdown drive, converting a third-and-6 play with a 9-yard pass to tight end Jason Witten and a third and 9 with a 21-yard pop screen to rookie receiver Kevin Ogletree.

Tashard Choice, after lining up in the Wildcat formation, covered the final two yards for the score.

The Eagles countered with two second-quarter field goals from 45 and 48 yards by Akers, but spent most of the first half struggling badly in the passing game. McNabb completed just 6 of 14 passes for 88 yards in the first half. He was also sacked three times as the Eagles had to juggle their offensive line after Peters suffered an ankle injury with 3:47 left in the first quarter.

With Peters on the sideline, the Eagles moved Todd Herremans from left guard to left tackle, Nick Cole from right guard to left guard and inserted Stacy Andrews at right guard.

McCoy and fullback Leonard Weaver proved to be the most effective method of offense in the first half. The two combined for 68 yards on just 12 carries. A 17-yard run by McCoy set up Akers' first field goal, and the running game accounted for 41 of the 54 yards that led to Akers' 48-yard field goal with 1:38 left in the half.

The Cowboys, thanks to a 64-yard pass from Romo to Patrick Crayton, got three points back just before halftime on a short field goal by Nick Folk.

Ellis Hobbs' 96-yard kickoff return for a touchdown was nullified by a holding penalty on rookie Moise Fokou. Still, the Eagles moved the ball, highlighted by a 45-yard screen pass to McCoy.

It appeared as if the Eagles had taken their first lead of the night at the start of the second half when returner Ellis Hobbs returned a kickoff 96 yards for a touchdown, but a holding penalty on rookie Moise Fokou negated that big play.

A series of big plays followed as the Eagles put together their best offensive drive of the night. McNabb completed four of five passes for 73 yards, including a 45-yard connection to McCoy that went all
the way to the Dallas 15-yard line.

Two plays later, McNabb avoided heavy pressure and threw a touchdown to tight end Brent Celek, giving the Eagles their first lead of the night at 13-10.

Early in the fourth quarter that lead disappeared after cornerback Michael Jenkins intercepted a McNabb pass at the 45-yard line. Maclin grabbed Jenkins' facemask as the cornerback went to the ground and the 15-yard penalty gave Dallas the ball in Eagles territory and led to a game-tying field goal by Folk.

"I was expecting a different throw," Maclin said. "We weren't on the same page. There were just a lot of mistakes. But we still had a chance to win the game."

Contact staff writer Bob Brookover at 215-854-2577 or bbrookover@phillynews.com.