Washington Redskins Coach Joe Gibbs seemed ready for a long night of calculations as he fidgeted with an empty coffee mug late yesterday afternoon at Redskin Park.

The Redskins must trim 11 players from their roster today to reach the National Football League's final 49-player limit. Thus arises the time when the numbers game becomes a difficult deliberation among coaches, who ask such questions as: "Do we keep five running backs or six? Seven defensive linemen or eight?"

Gibbs made one decision yesterday, naming second-year man Bob Holly as Joe Theismann's backup at quarterback. But that hardly helps the numbers game, because the Redskins still have four quarterbacks on their roster.

"I agonize more on this--making the right choices--than anything else," Gibbs said. "This is probably as important a time as any for us."

The season opener against Dallas is one week away now. Some say that will be the Redskins' judgment day. "It's only one of 16," Gibbs keeps saying.

For 11 Redskins players, judgment day is here. Reserve quarterback Tom Owen seems vulnerable, after a poor preseason. Linebackers Geff Gandy and Quentin Lowry, talented players in tough competition, also face difficult numbers. Offensive linemen such as rookie Nathan Newton and newly acquired veteran Art Kuehn face similarly distressing numbers, as does defensive tackle Pat Ogrin.

And running backs Richard Williams, Reggie Evans and Clarence Harmon have lived in uncertainty for weeks, all competing for what appears to be the fifth and final running back spot.

Evans, 24, a first-year player, was tense yesterday, answering a reporter's call to his home on the first ring, in a slightly frightened voice.

"I thought it would be them," Evans said, referring to Redskins' officials. "I'm sitting here waiting. They said they might call tonight and let me know, either way. When the phone rang, I jumped."

Likely, Evans has won the fifth spot. He gained 94 yards on 32 carries and played well on special teams in the preseason. Harmon is a seven-year veteran, who gained only four yards and caught three passes in the preseason. Williams has been a disappointment, playing tentatively and gaining 78 yards on 27 carries.

But Williams' greatest number is this: he is a second-round draft pick and teams just don't like to cut high draft picks, although the Redskins did cut Carl Powell, a wide receiver drafted in the third round last year.

"We've tried to give the ball to Reggie and Richard in the preseason," Gibbs said. "We know what the other guys (such as Harmon) can do."

In a way that seems perverse only on the surface, injuries can help some roster decisions. Players who might contribute--though maybe not at the present--and who have suffered an injury, might be placed on the injured reserve list, allowing a team to retain their rights without the player counting on the roster. The injuries, of course, must be legitimate.

So many things figure into roster decisions, Gibbs said. Since wide receiver Art Monk is still sidelined with a strained knee ligament and is doubtful for Dallas (and possibly Philadelphia the next week), the Redskins might want to keep another receiver, for the time being, anyway.

This may help Mark McGrath make the team. He has caught five passes for 124 yards for a team-best 24.8 yards per catch average in the preseason. Then again, maybe it won't.

"Mark is one of those guys who gets open," Gibbs said of McGrath, who played two years with Seattle. "That whole receiver situation, with the complication of Monk's injury, will be tough to iron out.

"(Monk's injury) is something you can't ignore. We do have some flexibility there. (Running back) Nick Giaquinto can slide in there and (kick returner) Mike Nelms can play (receiver), too."

Holly, who played at Princeton, clinched the No. 2 quarterback spot with his play in Saturday night's 27-19 preseason victory at Buffalo, He played the second half, completing nine of 16 passes for 124 yards and one touchdown.

"Last year, we spent the whole year in limbo, not sure of our (reserve) quarterback situation," Gibbs said. "Bob had about two bad plays (against Buffalo). But I think he showed steadiness. He was much more relaxed than I have seen in the past. I picture Bob as a steady performer."

Such words of confidence make Owen vulnerable. The Redskins will keep only three quarterbacks. There exists a theory among Redskins officials that, if Holly can be trusted in a critical game situation, than the Redskins can afford to bring rookie quarterback Babe Laufenberg along slowly. If they had not gained trust in Holly, they might have required Owen's experience. Owen is in his 10th year as an NFL reserve.

But Owen did not have a productive preseason, completing five of 11 passes for 46 yards with one interception.

Gibbs said he is concerned about injuries suffered Saturday night by linebacker Monte Coleman (deep thigh bruise), defensive end Dexter Manley (sprained left ankle) and defensive tackle Perry Brooks (groin pull). He also expressed concern over tight end Clint Didier's sprained ankle, suffered Aug. 19 against Miami. "It will be a wait-and-see type thing for all of them," Gibbs said.