Analysis came easily to Washington Redskins Coach Joe Gibbs yesterday, one day after the Dallas Cowboys had come on so hard in the second half to post a 31-30 season-opening victory at RFK Stadium.

Six plays, Gibbs said, cost the Redskins a game they had led, 23-3, at halftime. "Two by the defense, two by offense and two by the special teams."

Before breaking down the plays, though, Gibbs was certain to note that, even in an 0-1 start, promise can be found.

"We told the players today that if you play each week like you did last night, we'll win," he said. "When you play well, then you show the players on film, we show them potential."

The Redskins dominated the Cowboys in the first half. Mark Moseley kicked three field goals. John Riggins ran 18 times for 64 yards, with a one-yard touchdown. Quarterback Joe Theismann, so efficient completing 28 of 38 passes for 325 yards in the game, threw a 41-yard touchdown pass to Charlie Brown.

The defense held Dallas quarterback Danny White to one completion in nine passes that half. Punter Jeff Hayes put all three of his kicks inside Dallas' 20. Most definitively of all, the special teams did not allow Dallas to start one of its first 10 possessions beyond its 21.

The two defensive breakdowns to which Gibbs referred came in the third quarter. That's when White threw two touchdown passes to wide receiver Tony Hill, the first for 75 yards, the second for 51. The latter closed Dallas to 23-17 with 6:35 left in the quarter.

Include Tony Dorsett's 77-yard first-quarter run to the Washington six, which set up a field goal, and, as Richie Petitbon, coach of the defense, said, "They made 203 yards on three plays, for two touchdowns. When you play Dallas, you know they'll make the big plays. You just try to eliminate the touchdowns."

The 75-yard touchdown pass was made possible when Hill sprinted down the left sideline, then curled deep over the middle past cornerback Vernon Dean. Hill caught the pass, then sprinted the last 31 yards to the end zone unimpeded.

Turns out, the Redskins called out a change of defenses at the line of scrimmage. But Dean didn't hear it.

"I was playing a different defense than everyone else," said Dean, who said he was so bothered by the play that he stayed awake all night. "I thought I'd get help from the free safety (Mark Murphy) deep and over the middle. As it turned out, I was supposed to take the middle."

Petitbon said the Redskins thought the Cowboys might pass to the tight end on this play. "They gave us a short (yardage) look on the play," he said. "(The touchdown) is probably our fault as much as anyone's. With all the noise out there and all the fast motion, we should have stayed with our huddle coverage."

On Dallas' next drive, White threw to Hill as he sped down the right sideline with nickel back Anthony Washington on his heels. Though the coverage was tight, Hill caught the ball at the Redskins' 20 and, as Washington fell, again scored unimpeded.

"There's a case where Anthony was in good position," Petitbon said. "He just missed it. We should have had a safety there."

The two offensive breakdowns, Gibbs said, were penalties that stunted Redskins drives. After Dallas had closed to 23-10 with 12:20 left in the third quarter, the Redskins drove to a third and one at Dallas' 26. Riggins, held to 25 yards on nine carries that half, ran two yards for what appeared to be a first down.

But tight end Clint Didier was penalized for holding, moving the ball back to the 37. Theismann was sacked for a 10-yard loss the next play and the Redskins--out of Moseley's field goal range--had to punt.

The next offensive breakdown came with 10 minutes left. Again, the Redskins were on the move. Now the score was 23-17. On third and five, Theismann hit tight end Don Warren over the middle for an eight-yard gain to Dallas' five.

But Warren was penalized for offensive pass interference, moving the ball back to the 24. One play later, Moseley attempted a 31-yard field goal that could have given the Redskins a 26-17 lead.

But Moseley missed. His miss was as crucial as it was unusual. In 10 years with the Redskins, he has made 110 of 134 field goal attempts--82 percent--from inside the 40.

The two special teams breakdowns also were penalties. First, linebacker Stuart Anderson was caught blocking illegally on a second-quarter kickoff return that left the Redskins on their 13, nullifying Mike Nelms' 24-yard return. Nelms also dazzled the Cowboys with five punt returns for 74 yards.

The second came after Dallas had marched 80 yards in 12 plays, the last White's one-yard touchdown run that created a 23-23 tie with 2:25 left to play. (This drive was aided by linebacker Mel Kaufman's 15-yard penalty for spearing, which moved the ball to Washington's 35.)

As Rafael Septien kicked the extra point, for a 24-23 lead, rookie cornerback Darrell Green tried to block the ball. He missed and fell into holder Glenn Carano (Redskins coaches said films showed Green was blocked into Carano).

The Redskins were penalized five yards on the kickoff, which Septien put into the end zone for a touchback.

"Those five yards made a difference," said Wayne Sevier, special teams coach. "It took Mike Nelms out of the play. And the way Mike was going . . . Sure, he might have taken the ball only to the 20, but he might have taken the ball to the 50."