An untold truth escaped through the smiles yesterday at Redskin Park. It seems Coach Joe Gibbs was so angry during his halftime speech at Texas Stadium Sunday that he threw a locker room chair.

For shame.

"I don't remember whether I did or didn't," Gibbs said. He wore a silly grin that seemed to spell out, tooth by tooth: Washington 30, Dallas 28.

Then, Gibbs said, "I don't think that had anything to do with the way we played in the second half."

Perhaps after considering how the Redskins had rallied from a 15-point halftime deficit to a victory that granted them sole possession of first place in the NFC East Division, Gibbs chuckled and said, "I would have started out by throwing a couple chairs before the game, if I knew (the players' reaction)."

"I think it fired a lot of guys up when he did that," all-pro left guard Russ Grimm said. "I know it fired me up."

So, once again, perspective comes sunny-side up for the Redskins. They are 10-5 and hold a one-game lead over Dallas, the New York Giants and St. Louis with one game left in the regular season.

The winner of the Redskins-Cardinals game Sunday in RFK Stadium will get the division title and the home-field advantage for a first-round playoff game. It's mathematically possible the Redskins could lose to St. Louis and still win a wild card playoff berth.

"I think I've got it all figured out," Gibbs said. "Beat St. Louis."

Many of his players said that the most enduring memory of last Sunday's game will be cornerback Darrell Green's 32-yard return of an interception for a third-quarter touchdown.

There were other views, though. Said linebacker Monte Coleman, "I think people will remember this as the year we swept Dallas for the first time (in a regular season)."

"I think people will remember our refusal to quit," veteran defensive tackle Perry Brooks said. "It was an all-time great. It had to be one of the elite ones."

"I think they'll remember how Dallas was up, 21-6, and we came back," said defensive tackle Darryl Grant. "And they'll remember Art Monk's reverse (for an 18-yard gain on the game-winning drive)."

Grant admitted he will have another memory all his own. "I went home (Sunday night) and saw the game on videotape and I saw that John Madden (of CBS) kept confusing me with Darrell Green. In the first half, I heard him say, 'Darryl Grant got beat on that one.' He meant Darrell Green."

Grant nodded and said, "But there was no doubt which one was Darrell Green by the end of the game."

About the only glum note sounded yesterday centered on how the Cowboys sacked quarterback Joe Theismann eight times. Gibbs admitted he was surprised by how drastically the Cowboys altered their defensive set. It caused havoc for the Hogs on the line.

Dallas' defensive changes, also, were quite unlike those made earlier this season by St. Louis and the Giants. Those two teams wanted to stop the run first, then the pass. The Cowboys wanted to stop the pass first.

"I think they were taking a chance that (fullback) John Riggins wasn't healthy because he had been in the hospital," said tackle Mark May. "That's probably why they concentrated on stopping the passing game. It worked in reverse -- they stopped the passing game for a while, but it caught up to them. And John was healthier than they thought (running for 111 yards and one touchdown)."

The Redskins were held to 299 yards, 62 below their net average. The Cowboys often used a five-back, two-linebacker defense on first down, straying from their standard flex defense. Usually, they replaced linebacker Anthony Dickerson with safety Bill Bates, who covered the H-back, or motion tight end, Clint Didier. Or, Bates blitzed.

"(The Cowboys) made up their minds that they would give us the run, which I didn't think they would do," Gibbs said. "And they wanted to take away the outside portion of our passing game.

"The only way they could do that was to play a form of nickel, which they had never done before. On a running down, I never dreamed we would see five DBs (defensive backs) in the game at the same time that John Riggins was in the game. But they did that.

"And I would never, not in my wildest imagination, picture Dallas being out of the flex on running downs. There are some things that you can count on in football and that's one of them.

"Nothing is sacred anymore," he said.

Gibbs felt the Cowboys altered their defense likely because they expected the Redskins to use a three-wide-receiver formation of Art Monk, Calvin Muhammad and Charlie Brown. It was a logical expectation, too, considering how a similar set generated a 31-10 victory in Dallas late last season.

In fact, Gibbs admitted, he planned to use a Brown-Monk-Muhammad combination for "50 percent" of this game, until a knee injury forced Brown to miss practice Thursday and Friday.

So Gibbs put Didier in the starting lineup, in place of Rick Walker. Didier often lined up as a third receiver, split wide. As the Cowboys' blitz count rose, though, Didier often moved closer to the tackle, to add blocking.

This has been a difficult season for the Hogs. They have yielded 42 quarterback sacks, after having yielded just 35 in the 1983 regular season.

"No, it hasn't been a good season for us," all-pro left tackle Joe Jacoby said. "But it hasn't been a bad one, either. It's hard to put into words. (The linemen) have had so many ups and downs this year. The downs came in that first St. Louis game (a 26-24 victory for the Cardinals in which they blitzed often, getting four sacks). That's the game where we lost Jeff Bostic (the all-pro center, who incurred a season-ending knee injury).

"The ups have come in our first game against Dallas (241 rushing yards) and the New England game (235 rushing yards in a 26-10 victory) and now in the comeback against Dallas. It was hectic . . . "

Gibbs said "five or six" of the Cowboys' eight sacks came on blitzes. He said the Hogs weren't totally to blame because running backs often missed blitzing Cowboys. Also, Gibbs was sure to note that the Redskins exploited blitzes for several big plays, one a 14-yard pass to Monk to the Dallas one-yard line on the game-winning drive. Another was the 22-yard scoring pass to Muhammad in the third period.

And, Gibbs added, the Redskins will spend a great deal of time working against blitzes in practice this week.

The Hogs weren't helped when Grimm missed most of the second half. He received a laceration on his left eyelid that required six stitches and an eyeball contusion when defensive tackle Randy White's thumb came through Grimm's facemask. This caused a shuffling of linemen, George Starke coming in at right tackle, May moving to right guard and Ken Huff moving from right guard to left guard.

"That was a tense time," center Rick Donnalley said. "Everyone was alert, making sure all the offensive linemen were on the same page. Maybe it revealed our true character."

Grimm, whose eye was discolored and swollen shut, was examined by an eye specialist yesterday. "He said the swelling should go down in two-three days. Oh yeah, I'll play against St. Louis," Grimm said.