With their sputtering season clearly on the line, the Dallas Cowboys' defense made a magnificent stand at Texas Stadium today. Intercepting five of Dan Marino's passes, the unit ruined the veteran quarterback's first on-field appearance in six weeks as well as Miami Coach Jimmy Johnson's not-so-triumphant return to a venue that had given him so many memorable moments earlier in the decade.

Though Dallas mostly was inept on offense despite quarterback Troy Aikman being back in the starting lineup, linebacker Dexter Coakley and cornerback Deion Sanders had two interceptions each for the home team. All the Cowboys concurred that Coakley's 46-yard touchdown return midway through the third quarter turned the game in their favor.

Aikman, out the past two games because of a concussion, sealed the 20-0 victory with a 65-yard touchdown pass to big-play maker Rocket Ismail midway through the final quarter for a breathe-easy score.

Johnson had coached the Cowboys to two Super Bowl victories in five tumultuous years here before leaving after the 1993-94 season. This Thanksgiving day game marked his first return to the stadium where he made the expression "How 'bout them Cowboys?" his signature reaction to any big victory. Today, he must have been thinking, "How 'bout that Cowboys defense?"

"This is a difficult place to come in and play, as you know," Johnson said. "Obviously it was a difficult game for us. We had our opportunities, and we didn't take advantage of it."

The Cowboys, 6-5 and still very much alive in the NFC East race, took full advantage of an obviously rusty Marino. The most prolific passer in NFL history matched his personal worst of five interceptions in one game, an ignominious feat he hadn't accomplished since a 1988 game against the New York Jets.

Marino hadn't played since Oct. 17, when he was forced to the sidelines with a bone spur in his neck. He was replaced by Damon Huard, who won five of six starts before talking a seat this afternoon until the final two minutes, when all was lost.

Marino, who Johnson said would remain the starter, had only two days of practice with the first unit this short week. It clearly showed in a performance that seemed far more appropriate for a nervous novice than a 17-year veteran and future Hall of Famer.

"They didn't do anything we didn't expect," Marino said. "We really didn't adjust to anything either. I didn't make good decisions. It was missing. It was a timing thing. We were trying to make something happen offensively, but I wasn't doing the things to give us a chance to win. I had two practices before this game. I'm not making excuses, but it's going to take some time to get back into the rhythm."

It had better not take too long. The Dolphins fell to 8-3 today and out of a first-place tie in the AFC East with the Indianapolis Colts, 8-2 and playing the visiting Jets Sunday. The Colts travel to Miami for a pivotal game Dec. 5.

The Cowboys needed this victory to stay within striking distance of the Washington Redskins, still in first place in the mediocre NFC East with a 6-4 record going into Sunday's game against the Philadelphia Eagles at FedEx Field. The Cowboys are 5-0 at home, and as safety George Teague said: "It would be nice if we could find an invention to get some wheels put on this place and take it around with us. But we've got to start winning on the road."

Aikman said he felt no effects from the concussion three weeks ago, and Ismail also left the game with a mild concussion early in the first quarter. He was cleared to play by team medical staff early in the second half and finished with five catches for 125 yards, including the 65-yarder for his sixth score of the season.

Aikman finished with 232 yards passing and no interceptions, and running back Emmitt Smith had 103 yards on 31 carries. But dominating defense was the story for the Cowboys.

Cowboys defensive coordinator Dave Campo said he challenged his unit over the past two days by telling them "there were two defenses playing out there, but only one was being talked about, and it wasn't us. We talked about building a legacy for ourselves, especially with the younger guys. Maybe it started today."

The Dolphins had plenty of scoring opportunities, but place kicker Olindo Mare missed three field goals, including one partially blocked. And Marino made a dreadful blunder in trying to throw into double coverage in the Cowboys end zone, resulting in Sanders's first interception, in the second quarter.

Neither team could score in the first half, but Coakley changed all that with the first of his two interceptions. On third and seven at the Miami 41, Marino was aiming over the middle for rookie fullback Rob Konrad when Coakley swooped in, caught the ball and ran untouched to the end zone for a 7-0 lead that clearly inspired his teammates.

"We were in a zone blitz, and I don't think Dan saw me buzzing around back there," Coakley said. "It's my best game as a professional football player. It's a great Thanksgiving. I got two off a guy who will be in the Hall [of Fame] on the first ballot. It's very special to me."

Sanders also was delighted with his play and not the least bit shy about insisting: "I had a feeling it was going to be a tough day for Marino. He hadn't been in there for a while, and we played a great defensive game."

Asked if he thought Marino had lost some speed on his fastball after such a long layoff, Sanders said: "The two he threw to me came in there pretty good. . . . Everyone knew the big play was going to come. I was praying I was going to make it. I was hoping it would come on a punt return.

"We're playing great games at home. We have three left here, and we should capitalize on that. But when we're on the road, pray for us."

CAPTION: Deion Sanders points way for defense after first of two interceptions. Dallas intercepted Dan Marino five times.

CAPTION: Cowboys' Brandon Noble takes down Dan Marino, who had not played since Oct. 17, when a bone spur was revealed.