In the heady, humid days of early August, when every football team is undefeated and every practice play goes for a mock touchdown, the memory of that devastating afternoon last December in Dallas has begun to dim for the Redskins.

Roger Staubach's pinpoint passes don't sting quite as much anymore, nor is there as much talk about the emptiness that resulted from being so excruciatingly close to a playoff spot, yet still falling short.

But is this new-addition Redskin team that Coach Jack Pardee is molding so carefully in the long hours of training camp improved enough in just seven months to be immune now from a repeat of a similar fourth-period defensive collapse.

Or is Washington still vulnerable to the same kind of offensive explosion that Roger Staubach used to pull out the 35-34 victory and break the hearts of thousands of Redskin fans?

"You never can rule out a quarterback getting that hot again," middle linebacker Neal Olkewicz said. "But just the fact Roger Staubach isn't around anymore makes something like that seem improbable to me. Who else but Roger could play like that? Our defense was good enough; he was just incredible."

The imprint left by Staubach's heroics is still fresh in the Redskin's minds: two touchdown passes in the final 140 seconds, seven completions in his last 10 tries, 134 passing yards in just a fraction of one quarter.

But Staubach's damage wasn't confined to those brief moments. He finished with a stunning 336 yards in the air and was 24 of 42 for the game. That day the Redskin defense wouldn't let the Cowboys get untracked on the ground, but the magnificent Dallas quarterback found openings through the air that 1980 Redskin opponents are certain to see when studying films of the game.

"We've looked at those films, too," said Richie Petitbon, secondary coach.

"It really wasn't one of our better games defensively, but it also wasn't indicative of that many things. You've got a hot quarterback who gets some momentum going and it's very hard to stop him.

"To win in this league, you just can't have bad games. We had three or four last year on defense and that's too many. We just have to cut down on our inconsistencies."

At the halfway point of this training camp, two facts about the Redskin defense are emerging: it's better than last year, but it also is fragile enough, both in terms of depth and quality, to be vulnerable if injuries hit the unit or certain key players have off years.

The importance of injuries can be seen by a glance back at the Dallas loss.

Safety Ken Houston was out with a broken arm and did not play that game, reducing the club's defensive secondary flexibility. With Houston healthy, Petitbon says, "Roger would never have continued like he did." But with Houston sidelined, the Redskins were unable to alter their nickel defense by switching around personnel and Staubach was able to get the same defensive read play after play.

"You have to remember that Brad Dusek and Neal Olkewicz also came up limping before the game ended." Coach Jack Pardee said, "If we had been completely healthy, we would not have lost. But we weren't, and that's why I never felt safe the whole game."

The Redskins used the offseason to try to increase their defensive depth and cut down their susceptibility to injury. That was one reason for the Jeris White trade with Tampa Bay. He was an experienced cornerback who could aid the nickel, provide extra quality and strengthen an already veteran secondary. As long as White, who is holding out over a contract dispute, stays out of camp, the secondary suffers accordingly.

More depth should be provided by the addition of safety Mike Nelms, a star in the Canadian Football League, where he had 10 interceptions last year.

"You can't go to war anymore in this league without a really good secondary," said Pardee, "no matter who the quarterback is. We played a lot of people in the secondary last year and we plan to do it again this year."

Pardee's concern about pass defense also is reflected in the experiment involving Rich Milot, who is being tried in the middle after a rookie season at outside linebacker.On passing situations, he is being paired with linebacker Monte Colman. Pardee says those are his two best cover men at linebacker.

"Rich is also good against the run, so we are covered both ways," Pardee said. "But if he can adapt to the middle, we'll have another plus for out pass defense. It will make it harder for anyone to exploit the middle on us." p

The effects of the Dallas loss likewise are reflected in the emphasis the Redskins have been placing on a pass rush during camp. The rush all but collapsed in the fourth period against the Cowboys. Only Perry Brooks came close to sacking Staubach. The lack of sacks is something the Redskins always refer to as a key factor in the loss.

"We must have a better rush, no queston about it," Doc Urich, defensive coordiator, said. "A guy like Perry Brooks needs to develop for us. We have to have pressure from the inside and not rely solely on Coy Bacon to sack someone from the outside."

Brooks is being given every chance to win a starting job -- "He says he wants to be more than a spot player, and we'd love that too," Pardee said -- in order to bolster the interior rush. Urich likewise hopes to free tackle Dave Butz for more aggressive pursuit of the quarterback, so Butz can improve on his three-sack output of last season.

But what if Bacon, the premier sacker, gets hurt this season? Or if Brooks fails to step in as the Redskins hope?

"Sure, we are worried about what happens to the line," one team source said. "The defensive line isn't as deep as it needs to be. It's more vulnerable to injury than any place on the club except offensive tacle."

Right now, veteran Joe Jones -- second last season in sacks -- and rookies Mat Medenhall and Mike Matocha are the reserve ends. Neither youngster is ready to step in, so Jones must be impressive enough during preseason games to maintain his backup role. If Brooks falters, then veterans Diron Talbert and Paul Smith, both better against the run than rushing the passer, will be called on.

Pardee is quick to point out that maturity alone should make the defense tougher. Staubach, the wise one, picked on two younsters in particular: Coleman and cornerback Ray Waddy. Both, says Pardee, "profited by the experience and are better right now than they were in December."

Coleman, the team's prize linebacker and its best athlete, was matched in the fourth quarter against the wily Preston Pearson. The veteran Cowboy, a master at running patterns out of backfield, taught his young opponent some to the intricacies of playing defense in the NFL that afternoon. Pardee doesn't think Coleman will make the same mistakes again.

"He does things covering passes that linebackers don't usually do," Pardee said. "He'll get beat, but not too much."

Waddy had most of his problems tackling loose Cowboys. During the offseason, he has grown bigger and stronger and his tackling has improved immeasurably.

"You figure that Rich Milot and Neal Olkewicz will be better, too, through experience," said free safety Mark Murphy, just beginning his second year as a starter. "There is nothing like getting out there and playing to help you understand what you are supposed to do. I know that I feel a lot more comfortable this season.

"You can feel the change in the defense, and the whole team for that matter, in camp. There is a quiet confidence that we have from last season, despite the Dallas loss. No one thinks we lost that one. It was a fluke.

"But one thing we did learn. We have to put a team away once we are up on them. It happened a few times last season and we can't let it go on. I think that will come with maturity too. You profit by your mistakes."

That's one lesson Pardee hopes the team also learns from the Dallas loss. "You can't celebrate too early," he said. "Remember, that was the top offense in the conference we were playing against. They scored a lot of points. But I still like our matchups against them. We know pretty much what to expect."

In a month, the Redskins get a rematch with Dallas before a Monday night television audience in their home opener in RFK Stadium. Petitbon says that the best thing that could happen for Washington's defensive unit.

"It's like a fighter coming right back after a knockout," he said. "You want to get right back in there and go after the guy again. It will wipe out any doubts we may have about ourselves."

And, he added with a smile. "We'll find out first hand how Danny White compares with Roger Staubach."