The Redskins have taken the mystery out of losing. Even yesterday, when they had all the motivation any team ever could want, they still were unable to eliminate the same devastating penalties, errors and poor tackling that have turned this season into a chaotic nightmare.

The Eagles prevailed, 24-0, and for the third straight week, the Redskins were all but defeated by the end of the first half. This time, they spotted Philadelphia a 17-0 lead at intermission, allowing the Eagles the luxury of cruising to a victory that hardly appeared to test their full abilities.

Owner Jack Kent Cooke told the Redskins and their coach, Jack Pardee, that he wanted to see an improved will to win. The players insisted they performed with more effort and desire. But the result, said center Bob Kuziel, "was we self-destructed even when we tried too hard. Even that seemed to backfire on us."

Yet there was little evidence of great emotion by the players, save for their constant jawing at the surprised Eagles.

To make matters worse for Pardee, quarterback Joe Theismann pulled a hamstring muscle in the first half and could barely move by the fourth period, when he finally was replaced by Mike Kruczek. Theismann, the Redskins' most valuable player, said he wasn't sure if he could play next week against Dallas. "We'll just have to see how it progresses, but it hurts right now," he said.

Meanwhile, the negative numbers keep mounting. Washington is 3-8, its worst record at this stage since 1963. This was its second shutout of the season, the most since 1961 and the first time the Redskins ever have been blanked twice at home in the same season. The Redskins suffered their fourth loss at home this year, the most since 1968. The defense now has given up 98 points in the last three games, all defeats, while the offense has scored just 35. And the Redskins have managed only 16 points in the first half of the last four games, compared to 82 for their opponents.

Pardee apparently is safe for the rest of the season, according to what Cooke said yesterday.

With the Cowboys coming up on Sunday, there appears no end to the Redskins' woes. Pardee said yesterday it "would take a little time to work our way out of it.

"This didn't happen overnight and we won't snap out of it overnight. We need to have some stability and I have that stability and I know what it takes to get out of this.

"It's not that they don't want to win. We just killed ourselves every way in the world: penalties, pass protection not holding up, turnovers in the scoring area. We have to stop letting teams get off to a quick start like that."

But how does Pardee correct the problems? Last week, the defense was defenseless against the Bears. This week the offense sputtered and stumbled, losing two fumbles and three interceptions that led to 17 Eagle points. And the club remains the most penalized in the league, adding another six infractions yesterday plus a couple declined by the Eagles.

"We shouldn't have those mistakes at this stage," Kuziel said, "but veterans are making them. How do you explain that? We are killing ourselves and we aren't going to win until we stop making the same errors over and over."

The Redskins said they came out of the locker room determined to upset Philadelphia and take the mounting pressure off Pardee. But if the Eagles were singed by Washington's fire, it didn't show.

They merely took the opening kickoff and methodically drove 81 yards on 12 plays to take a 7-0 lead, the touchdown coming on a seven-yard pass from Ron Jaworski to tight end Keith Krepfle. Then, after cornerback Richard Blackmore picked off a Theismann pass on Washington's third play of the game, Jaworski quickly found reserve tight end John Spagnola for a 14-yard score.

The game was only 11 minutes old and Philadelphia already was ahead, 14-0. At that point, the Eagles had run 18 plays and gained 122 total yards. The Redskins had run three and picked up five total yards.

The Eagles, now 10-1 for the best record in the league, built their early lead with the help of Wilbert Montgomery, the premier running back gaining 50 yards on 12 carries before going out reinjured in the second quarter of his first game back from a long layoff with leg problems."We kept trying after that," Pardee said in a moment of candor, "but the damage already had been done."

For most of the next 49 minutes, it became a matter of watching Theismann try to survive against the Eagle defense, the best in the National Football Conference. Six times, he had the Redskins in Eagle territory, but he could get them inside the 30 just once (to the 24), thanks to a combination of a heavy pass rush and Washington's constant mistakes.

In the first half, the Redskins had four first downs wiped out by penalties, including one on guard Jeff Williams for being downfield on a 12-yard pass to Art Monk and another on Kuziel for tripping that nullified a nifty end sweep by Ike Forte.

The Redskins' most embarrassing moment came early in the third period on back-to-back plays. On a third and one from the Eagle 36, Theismann handed off to fullback Buddy Hardeman, who stopped and lofted a balloon pass toward Monk, who had broken free at the 10. The ball floated and floated, finally coming down on Monk's fingertips.

"It was just an inch or two overthrown, it was just over my fingertips and I couldn't pull it in," said Monk, who dropped the ball as he went into the end zone.

So on fourth down, Pardee went for the first down. Halfback Wilbur Jackson, who had some success sweeping the Eagle ends, started toward the right side. But the Eagles' Carl Hairston, who gave tackle Fred Dean trouble all day, stormed into the backfield and pulled down Jackson from behind.

To make matters worse, Jackson fumbled. Linebacker Jerry Robinson picked up the ball, but he thought the play had been blown dead. Then teammate Bill Bergey told him, "Run, run, run." So Robinson sprinted down the sideline with a limping Theismann in pursuit. It was no contest and Robinson scored on the 59-yard scramble for a 24-0 Eagle advantage.

Theismann had hurt his leg on a first-quarter sack and his attempt to catch Robinson severly aggravated the injury. His mobility was reduced and, instead of being able to scramble, he had to stay in the pocket and either absorb sacks (three in all) or unload hurried passes.

The result was one of his poorer days: 16 of 34 for 164 yards and three interceptions. He also once tried to throw away a pass, and, true to Redskin form this year, he had it intercepted by rookie Roynell Young in the end zone. Young outleaped Monk on the play, ending that Washington threat.

"Hey, this isn't Joe Walton's fault," Theismann said, defending the Redskin offensive coordinator. "He isn't playing out there. It's not the weapons that are messing up, it's the marksmen. It gets really bad to keep looking up at the (first down) stakes and seeing first and 20 all the time. If you are Joe Walton, what do you call in that situation? It's not easy.

"I'm so embarrassed by the way we're playing that I don't even want to talk to someone from the other team."

Theismann said he hurt his leg against Chicago last week and then tried to support himself with the other one today and it popped. "I thought it didn't affect my balance or my arm that much, but I would have gotten the hell out of the pocket a few times. I couldn't scramble . . . just couldn't sprint out."