For Coach Joe Gibbs, this is not a normal preseason game.

After two straight losses this summer, he thinks it is essential for the Redskins to beat Buffalo tonight at 7:30 at RFK Stadium.

"Preseason or not, if we keep losing the pressure is going to keep mounting," said Gibbs, who previously had played down the need for the Redskins to win in the preseason. "Besides, this is our only home game around five road games (three in the preseason, two in the regular season). We've got to take advantage of playing before our home fans."

For rookie quarterback Bob Holly, this is not a normal preseason game, either.

Holly, the little-known 11th-round draft pick from Princeton, is to make his Redskin debut in relief of starter Joe Theismann. With the acquisition Wednesday of Tom Owen from New England, Holly realizes this may be his only chance to convince the coaches he should be the team's No. 3 quarterback this season.

"I'm excited," Holly said. "I'm looking forward to playing. It's just been nice getting extra work in practice all week. Now I hope to have some fun.

"This is a change for me from nothing to something," said Holly, who received little practice time as long as he was playing behind both Theismann and Tom Flick, who was traded for Owen. "My lack of work hasn't enhanced my sharpness. But I've been watching carefully during practices and trying to learn as much as I can."

Holly says his aim tonight is "not to be a destructible force, but to contribute to the win and play as solidly as I can."

He already has seen how little patience the Redskins have with quarterbacks who are a "destructible force." Flick, once projected as their quarterback of the future, was traded abruptly after two miserable second halves in the opening preseason games.

Both Gibbs and General Manager Bobby Bethhard believe Holly has the potential to fill the void created by Flick's departure.

"We like what we've seen of him in training camp," Beathard said. "He's an intelligent guy who learns fast and has a good arm. We don't expect him to be great right away; that wouldn't be fair to him. But he has a future, no question about that."

Holly played in what he described as "a pretty complex offense" at Princeton, where he threw for 2,622 yards and 16 touchdowns his senior season. But now he is learning to "read more complex defenses and changes and getting used to terminology. The more I practiced this week, the more comfortable I felt."

It is likely that Holly, should he do well the rest of the preseason, will wind up on the newly instituted four-man taxi squad unless Gibbs decides to carry three quarterbacks on the active roster.

How much Holly plays tonight -- Gibbs said he wasn't planning to use Owens -- might depend on the performance by the rest of the Redskins.

Although Gibbs and his staff are still in the process of evaluating personnel, the coach also might be tempted to use his starters longer than he has in the previous two games. Those regulars outplayed their counterparts from both Miami and Tampa Bay, only to have the reserves lose control of the games.

"We are concentrating on cutting down our mistakes," Gibbs said. "When we got off to a bad start last season we were making too many mistakes and now we are doing the same thing. We can't have more than one or two turnovers and expect to win.

"It's up to a coach to see both the good and the bad in games, and not just what has gone wrong. I really like the way many of our starters have played, especially against Tampa Bay. Now is when you are looking toward the regular season, trying to make sure everyone is ready to play when it matters."

Even though Buffalo (1-1 in preseason) was a playoff team last year, the Bills are not at full strength for this game. They are missing two of their brightest stars, halfback Joe Cribbs and receiver Jerry Butler, both of whom have contract difficulties.

Without Cribbs and Butler, Buffalo lacks much of its normal quickness, especially since reserve halfback Roland Hooks is sidelined with an injury. The Bills are expected to start two fullbacks, Curtis Brown and Roosevelt Leaks, in their backfield tonight.

The game also marks the return of cornerback Lemar Parrish to RFK. Parrish, who was an all-pro as a Redskin, was traded to Buffalo on draft day last April for a fifth-round choice.

Parrish has been bothered by a sore lower back during training camp and currently is a reserve.

The Redskins dealt off Parrish after picking Vernon Dean on the second round. Dean, who probably will be a nickel back this year, had his difficulties last week against Tampa Bay. But Richie Petitbon, the Redskins' defensive coordinator, said he remains convinced Dean is a fine prospect.

"Not eveything that happened to Vernon last week was his fault," Petitbon said. "But even when he made mistakes, he showed me something by coming back and finishing off real well. He had every reason just to pack it in and he didn't. He's going to be a player, I'm sure of that."

Receiver Virgil Seay (split finger) isn't expected to play. He'll probably be replaced by Charlie Brown . . . Nick Giaquinto (sprained ankle) also is questionable . . . Gibbs said one of the major highlights of training camp "was that we suffered no major injuries. Everyone who was hurt should be able to come back soon."