In trying to explain the Redskins' roller-coaster season, in which they have followed splendid victories with some incredibly lackluster defeats, Coach Jack Pardee always points to one reason: "Our small margin of error."

Pardee has had to live with this problem on film, in meeting rooms and on the playing field since the start of training camp. And that is why he and his staff have put together a cautious offense complemented by a sometimes daring defense.

Statistics back up Pardee. After 13 games, a definite pattern has developed that readily distinguishes all Redskin victories from their defeats. dSave for a couple of exceptions, this club wins and loses for the same reasons: number of mistakes, scoring efficiency, rushing defense and sacks.

Statistics also point up a major offensive difficulty. There is no Redskin ranked among the top 20 NFL receivers and none among the top eight runners, giving Pardee and Joe Walton, the offensive coordinator, limited weapons to strike quickly.

That offense has a unique position in the league. It remains the only one on a winning team that is being outgained in total yards by the opposition (3,674 to 4,093).

Washington must grind out points, which sometimes has proven troublesome, or hope for turnovers and then capitalize on errors, which has happened frequently.

Almost every other playoff contender in the NFL can boast of at least one game-breaking runner or receiver. Many, like Pittsurgh (Franco Harris, Lynn Swann, John Stallworth) and Dallas (Tony Dorsett, Tony Hill, Drew Pearson) have both.

Chicago is gifted with Walter Payton, New Orleans with Wes Chandler, New England with Harold Jackson, San Diego with John Jefferson, Houston with Earl Campbell and Ken Burrough, Cleveland with now-injured Greg Pruitt, Miami with Nat Moore and Philadelphia with Wilbert Montgomery.

"Great athletes can turn things around for you even on days you aren't playing well," Pardee says. "A little pass over the middle to a Dorsett can turn into a touchdown even when it should be stopped for a five-yard gain."

Lacking the game-breaking threat, Washington has gone about winning a different way. Its method begins with quarterback Joe Theismann and his short passing and power-running offense.

If Theismann was not having a superior season, the Redskins would not be on the verge of gaining a playoff spot. He has been the one consistent force on the offense and it is no accident that, on his best days, his team has won.

But even on his less-efficient afternoons, Washington remains competitive as long as it meets certain criteria;

The Redskin defense must generate sacks. They have 27 in their eight wins, and only five in their five losses. Their two best sack days -- seven against the Eagles and six against the Cowboys -- came in games where the entire club also played its best.

The club must create turnovers while keeping its own mistakes to a minimum. Washington leads the league in giveaway-takeaway ratio with 21 giveaways and 41 takeaways. The Redskins have intercepted 18 passes in wins out only five in defeats, while they have fumbled just four times in victories but lost an average of one ball per loss.

In six of the Redskins' eight triumphs, Mark Moseley has kicked at least two field goals. The Redskin offense is geared to maintain possession long enough for him to have a kicking try. In three of five losses, he has been limited to one or no successful kicks.

The Redskins have shown they need to score at least 13 points in a game to have a shot at winning. Thus, it becomes vitally important for them to generate points every time they are inside the 10-yard line. In their wins, they have scored 12 touchdowns from inside the 10 but only six from the same area in their losses.

Opponents who have not been able to run the ball successfully on Washington usually have lost. In six of the eight wins, foes have gained fewer than 150 yards on the ground; four were held to under 114 yards.

Although Washington has faced a horde of talented runners this season, only Ottis Anderson has managed to gain more than 100 yards against them in games the Redskins have won. In Washington losses, Campbell, Mongomery and Billy Taylor all have gone over the 100-yard Mark.

The Redskins' ability to limit mistakes in their best games is particularly notable. Washington has had no more than one fumble in all but one of its wins (and no more than two interceptions) while causing the opposition to commit numerous errors.

"We've stressed from the very start that we had to be aggressive and swarm around the ball and cause mistakes while also protecting the ball ourselves," said Pardee. "It's paid off."

The Redskins added tight end Grady Richardson, a prodcut of Cal State Fullerton, to the active roster in place of Ken Houston. Richardson (6-foot-4, 228 pounds) has been cut the last two training camps by Washington, but Pardee says the former World Football League player can help immediately on special teams . . . In Green Bay, Wis., the Packers announced that quarterback Lynn Dickey will make his first NFL start in more than two years in Washington Sunday.