The Washington Capitals, who two weeks ago basked in the glory of the franchise's greatest victory, last night suffered their worst defeat of the season, 8-1, to the same team: the Philadelphia Flyers. In the process, Washington lost goaltender Mike Palmateer for at least a week.

Palmateer, who made 44 saves in the Capitals' 6-0 first-ever triumph over Philadelphia, hurt his left thigh midway in the second period making a split save. Further examination will determine whether the injury is a pulled hamstring or a torn muscle.

"It could be a week, two weeks or longer," said team physician George Hajjar. "It all depends on how he reacts to the treatment. We should be able to make a better determination by Tuesday."

This rematch was ill-timed for Washington, which trailed, 4-1 when Palmateer was hurt. Besides the memory of the Dec. 21 game in Phildelphia against Washington, the Flyers came into Capital Centre with a 1-4-0 record in their last five games, including an embarrassing 4-3 loss to Winnipeg Friday night.

Thus, Philadelphia wasted little time before a sellout crowd of 18,130, scoring on its first shot and remaining the only team not to have lost in Capital Centre (8-0-6), with a 20-1-6 overall record against the Caps.

Brian Propp, who later was to take the slap shot that would cause Palmateer's injury, scored 30 seconds into the game off a feed from Ken Linseman. Linseman personally ruined the Caps, assisting on three goals and scoring an unassisted second-period goal.

The Capitals failed to get a shot on goal for more than 10 minutes, but managed to tie the game, 1-1, at 17:12 on Archie Henderson's first NHL goal. But the Flyers took the lead for good 46 seconds later when Paul Holmgren scored a disputed goal. The Capitals protested that the Flyer right wing was in the crease when Propp's rebound shot hit him and went in.

"I thought we finally showed some life when Archie scored, but that questionable goal really hurt," said Washington Coach Gary Green.

After a peaceful first period, in which only three minor penalties were called, the game's, first brawl broke out at 6:33. The Capitals trailed, 3-1, after a Rick MacLeish power play goal, but Washington had the extraman advantage after terry Murray had been called for hooking.

As Referee Ron Wicks was signaliling a delayed high-sticking call on Bob Dailey that would have given the Capitals a two-man advantage, Ryan Walter scored. But Wicks disallowed the goal, Walter having used a high stick to score. At the same time, Mike Gartner went after Bobby Clarke and when peace was restored, 88 penalty minutes were assessed, 49 to the Capitals. Both teams had three skaters remaining.

When Linseman was called for interference less than a minute later, there were 15 men in the penalty box serving a variety of minor, major, bench and misconduct penalties. The teams finished with 146 minutes in penalties (76 for Washington) far below the 359 total of Dec. 21.

With both teams down to three skaters, both Dennis Maruk and Rick Green missed scoring chances for Washington before Bill Barber scored at 8:19 to give the Flyers a 4-1 lead. Following Palmateer's injury at 13:11, the Flyers assured their second victory here this season when Linesman and Tom Gorence scored 14 seconds apart, at 15:36 and 15:50, on Wayne Stephenson, still not fully recovered from a bruised thigh.

Palmateer's injury further depletes the Capitals, who open a four-game road trip in Edmonton Wednesday. The Capitals will need to bring up at least one goalie from Hershey, either Rollie Boutin or Dave Parro.

"I just don't know what we'll do," said Coach Green. "I haven't had time to think about it yet. But Mike's injury didn't affect the outcome of the game. They outplayed us from the very first shot. They definitely knew what they (the Flyers) came here for."