The stain on the Washington Redskins' stat sheet seems a little larger and a bit more conspicuous each week.

The unmistakable fact is this: for the first time since 1981, teams are running with success against the Redskins. Coach Joe Gibbs conceded yesterday, "It would be wrong on our part to just dismiss it. It's been creeping up on us each week."

This is hardly the Redskins' greatest concern in these days when the wind blows harder and their schedule gets somewhat softer.

The Redskins have stewed for hours and hours over how to overcome injuries, for example, and today, Gibbs said, the team will carry out its plan to reactivate free safety Mark Murphy from injured reserve and to place strong safety Tony Peters (abdominal muscle pull) on the same list, for a minimum of four weeks.

The Redskins' defense should not be considered in dire straits. It is, after all, still rated as the third-best run defense in the league, yielding 102 yards per game. That number should improve because the Redskins will play Sunday against Philadelphia, a team that has not found the wheels to make its running game budge this season (averaging 86 yards per game).

But the Redskins aren't accustomed to giving up rushing yardage in such large doses. A month ago, they were the league's top-rated rush defense, having spurred a five-game winning streak by limiting all those opponents under 100 yards rushing. The Redskins were giving up 79 yards rushing per game at that merry moment.

Since then, however, a downward spiral has occurred and suddenly the defense is giving up 4.1 yards per carry -- only the 19th-best mark in the league.

The Redskins gave up 120 yards rushing in a 26-24 loss at St. Louis, four games ago. Next, they yielded 130 in a 37-13 loss to the New York Giants, a team with a poverty-stricken rushing game.

Next, the Redskins gave up 148 yards rushing in a 27-14 victory against Atlanta. Gerald Riggs ran for 134 yards on 27 carries and the Falcons averaged 5.1 yards per rush.

And last Sunday, the Detroit Lions rushed for 169 yards in the Redskins' 28-14 victory at RFK Stadium. The Lions had only 22 rushing attempts and a remarkable 7.7 yards-per-carry average. It represented the Redskins' worst rushing yield since the Los Angeles Raiders rushed for 231 yards on 32 carries in the Super Bowl the Redskins would rather forget.

Put all of these numbers from the last month together and it's like letting loose a slingshot that rips into the ego of the Redskins' rush defense. It hurts.

And to think, only last season former Kansas City coach Hank Stram, now a television analyst, said that running against the Redskins was "like throwing popcorn at a battleship."

"We have got to do a better job. That's cut and dried," said defensive tackle Darryl Grant. "Earlier in the season, people put a lot of heat on us for not (developing) a pass rush. Perhaps we've neglected some of our techniques against the run recently. It's something that we have to correct."

The defensive coach, Richie Petitbon, said, "I think our problems have been that we've missed a lot of tackles and, in certain areas, we haven't carried out our assignments.

"I think the amount of yards we've given up have to concern us. If it continues, we'll have to take a real hard look at what's causing it."

Petitbon pointed out that many of the rushing yards achieved against the Redskins recently have come in two isolated situations:

* Short-yardage situations in which defenders are crowded near the line of scrimmage; somehow, the Redskins have allowed running backs to break free for big gains. Riggs totaled 57 yards off two third-and-one plays.

* Nickel situations in which a fifth defensive back is added on long-yardage situations to defend against the pass; offenses have used draw plays or quarterback scrambles to gain big rushing yardage, if not first downs, against the Redskins. The Lions, for example, gained 17 yards on a third-and-41 draw play; another time, quarterback Gary Danielson scrambled for 22 yards. These are big gains that, in a misleading way, disrupt the Redskins' rushing statistics.

"In short-yardage and nickel situations, you open yourself up for big gains on the ground," Petitbon said.

No, Petitbon insisted, he is not panicking at the situation. "If teams were consistently getting five yards a carry on us, that would really concern me," he said.