Joe Washington's ailing left knee was extremely sore yesterday, increasing the possibility that he may not be available for the Redskins' season-opening game against Philadelphia Sept. 12.

A final evaluation of the damage to the knee will not be made until Monday, when Washington will be examined by Dr. Stanford Lavine. The Redskins are hoping the knee will show sufficient improvement by then so that Washington will not have to undergo arthroscopic surgery.

If Washington does have surgery, it will be difficult, but not impossible, for him to be ready for Philadelphia. He already has been ruled out of Friday's final preseason game in Cincinnati.

"I'm more pessimistic today than I was Friday night," Coach Joe Gibbs said. "We were hoping he would be able to walk around okay today but it was very, very sore. Normally, that means something. I think there is a good chance that it will take a chunk of time to get better."

Washington hurt the knee on the last play of the first quarter in the Redskins' 20-14 loss to Buffalo Friday. He was cutting around left end when the knee gave out.

"I'm just going to wait and see how the knee progresses," Washington said. "Maybe they will have to 'scope' it and get it fixed up. But I'll do every little thing I can to get myself ready for the first game, if it's possible."

The loss of Washington for any extended period would be a blow to the Redskins, who already are trying to deal with an 0-3 preseason record.

Washington is by far the team's quickest back, and his presence gives the Redskins a much-needed extra dimension on offense. The team lost all five games that he missed last season, when he rushed for 916 yards and caught 70 passes.

"John Riggins will just have to carry a real heavy load if Joe is out," Gibbs said. "But, thank goodness, John is really smoking. He looks great. There is no comparison between how he looks now and how he was the same time last year. He was sluggish then. He's running now."

Riggins left Friday's game twice with a bruised knee, but he was cleared yesterday to resume playing, as was defensive tackle Dave Butz, who also has a knee bruise.

"We'll also need more from Otis Wonsley and Wilbur Jackson," Gibbs said. "We hope to get Nick Giaquinto (ankle sprain) back and he'll have to fill in for Joe's pass responsibilities." Jackson, who fumbled twice against Tampa Bay a week ago, did not carry the ball Friday.

Although preseason records and regular-season performance often have no correlation, Gibbs admitted he was especially concerned about Friday's loss because he used regulars most of the way in trying to win it, yet the Redskins couldn't pull out the victory even when Buffalo switched to a rookie quarterback in the last quarter.

In evaluating that game, Gibbs said:

The offense needed "playmakers, guys who put the ball into the end zone. We missed a lot of plays where we had the opportunity to win. I think we've got some guys who are playmakers, but we need to have some more produce."

He wasn't overly concerned about the breakdown in protection by the offensive line, which allowed five sacks. "Last year, I used to consider the protection when I called plays. This year, I don't. I have faith we'll get it worked out. Buffalo did an unusually good job with their defensive ends, who beat our tackles on occasion. That normally doesn't happen."

There isn't enough defensive consistency yet, even though he is pleased with an increase in aggressiveness. "What seems to be happening is that we go along good for six or seven plays and then, boom, something bad happens. They had four runs for 135 yards and another 30 that averaged 1.9. We just have to cut down on the big plays. We also aren't causing any turnovers, either."

Some of Buffalo's most effective running plays came after Butz went out. The Bills were able to rush up the middle against reserves, even though Buffalo's best halfback, Joe Cribbs, is not playing because of contract problems.

Gibbs said the Redskins would be working the remainder of the preseason "to get our level of play up. Sure, we're running out of time; that's what makes it tough. But we know we have to get better.

"We've played three very good clubs, teams that were in the playoffs, and it's helped us evaluate things well. What it means not to win, I don't know. What you would like to do is play everyone and win. We try to get the players to understand what it takes to win a game. For us, certain things keep coming up again and again."

Gibbs also said that the game's pivotal play, a fumbled punt by Mike Nelms that at first appeared to warrant a penalty on Buffalo, was judged correctly by the officials.

"Our guy blocked a Buffalo guy into Mike, just like the officials said," Gibbs said. "We had four stupid penalties on special teams that really hurt us. But, otherwise, the special teams played very, very hard."

Although rookie tight end Mike Williams played ahead of Rick Walker Friday night (along with Don Warren) in the Redskins' two-tight-end set, Gibbs said the staff has not made a final decision about that position.

"We're still in the process of evaluating it," he said. "We decided to give Mike and Rich Caster most of the playing time Friday. I told Rick Walker we knew what he could do and we wanted to look at the other two.

"Both played very well. Caster is coming back well from his knee injury and Williams is going to be a player in this league, no doubt about it."

Mark Moseley's left (nonkicking) foot was sore yesterday. The foot was stepped on during the game and his big toe was badly bruised . . . Gibbs said he was impressed with rookie Jeff Hayes, who made his debut as the Redskins' only punter Friday. Although Hayes did not have a consistent night, he wound up registering probably the game's best tackle, a hard-driving hit on a punt return in front of the Redskin bench . . . After a day off today, the Redskins will resume workouts Monday. They have to cut the squad from 70 to 60 players by 4 p.m. Tuesday.