Yesterday, the Redskins celebrated. They watched game films of Sunday's stunning 37-34 victory in Philadelphia and they cheered. Then they carried home free six packs of beers to help unwind on their day off.

This now is a team, Coach Joe Gibbs said, that "feels good about itself." His biggest concern? "Getting them back down to earth, so we can go back to work on Wednesday for Tampa Bay."

There was considerable praise for quarterback Joe Theismann, whom Gibbs said played so well "he'll make us a better offensive team if he continues the same way." Gibbs also was ebullient about the work of his special teams, and lauded receivers Art Monk and Charlie Brown.

Of course, not everything went perfectly in victory. Gibbs wasn't pleased with the spotty pass coverage -- "it has to get better and the players know it" -- and Wilbur Jackson's sore left knee could keep him from playing Sunday.

Still, there was a vastly different atmosphere at Redskin Park than the one the players encountered eight days ago, when they began preparations for the Eagles. That day, they were introduced to two significant offensive changes that most likely made the difference between victory and defeat.

The first change involved the offensive line, which had been struggling in exhibition games to protect Theismann. The linemen had been using man-on-man blocking since the start of training camp. Now, they were told, they would switch to zone blocking, much like they were using on running plays.

"We were having trouble with people stunting and blitzing on us," said Joe Bugel, the offensive line coach who had three practice days to work out the kinks in this "zone wall" approach. "We just decided going to a zone technique would be a better idea. We wanted to make use of our size. In a zone, you just have to guard the area to each side of you and not move that much."

At the same time, Monk was told he would be replacing friend Terry Metcalf, at least some of the time, as the receiver in motion in the Redskins' highly effective passing against nickel defenses. Metcalf, who was cut that day, had caught 48 passes last year, mostly as the motion man.

"We had been using Art in that role here and there throughout camp, but he probably just didn't realize it," Gibbs said. "We looked over our personnel and decided, at least for this one game, he would be the best person to put in the motion role."

Those decisions, made after six weeks of training camp and a 0-4 exhibition season, wound up being just what the Redskins needed.

Except for a first-half sack, when tackle Joe Jacoby couldn't stop defensive end Guy Brown, the linemen protected Theismann magnificently. Their performance was even more significant because the Eagles, who normally don't blitz, surprised the Redskins with several new stunts and moves by their linebackers. But the zone wall held.

"With man-to-man, we back up a couple of steps before we make contact with the lineman," Jacoby said. "With zone, we don't give any ground. We make our set immediately at the line. It allows us to be a lot more aggressive and physical. I really enjoyed doing it for the game, because it obviously worked."

Given extra time, Theismann had his best game as a professional: 28 completions in 39 passes for 383 yards, three touchdowns and no interceptions, all against the best defense in the National Football League last year, according to league statistics.

Monk caught only one pass as the long-yardage motion man, but it was a 28-yarder over the middle in overtime, when he broke away from linebacker Jerry Robinson and ran to the Eagles' 42. Four plays later, Mark Moseley kicked the winning field goal.

"I do so much motion anyway that I felt comfortable in the game," Monk said. "I'm sure there is more they can do with me in the (passing) package, but you can only put in so much in a week."

It was plays like that, Gibbs said, that are "the major difference between now and preseason. We had people open before and something would go wrong. Sunday, everything worked just right. We had big-play men. The result is this team has its confidence back, the same confidence it had at the end of last season. I think we now have momentum again. We know we can be competitive with good teams, and that's important."

The victory also eased concern over the pass defense, which allowed 371 yards despite unexpectedly good pressure by the four linemen. They got six sacks, the most in a game in two years.

Gibbs said the Redskins purposely blitzed less and played more zone schemes in the secondary in hopes of tightening the coverage. But Eagles quarterback Ron Jaworski completed 27 passes, in part because cornerbacks Joe Lavender and Jeris White still are not playing well.

"You always have to be concerned when you give up that many yards," defensive coordinator Richie Petitbon said. "We can play a lot better, and the improved rush will help us do that. Still, it wasn't as bad as it might have looked."

Gibbs said he expects Mark May (knee sprain), Mike Nelms (charley horse) and Russ Grimm (bruised ribs) to play Sunday. Jackson has not been ruled out, either . . . The Redskins now have won four straight regular-season games . . . Theis-mann's 400 yards of offense, 383 passing, 18 rushing, was a career high . . . The Tampa Bay Buccaneers have placed guard Ray Snell, their No. 1 draft choice in 1980, on injured reserve. Coach John McKay said Snell, who hurt his right knee in Sunday's 17-10 loss at Minnesota, would be unable to play at least six weeks. Teammate Gene Sanders, a tackle, fell on Snell's knee during a pile-up.