It was a day for smiles and jubilation at Redskin Park yesterday, so when someone asked Coach Jack Pardee who he will start at quarterback Sunday against the Eagles, he could not contain a robust laugh.

"I don't know if I'll announce it yet," he said, tongue planted firmly in cheek. "Let me think about it for a couple of days."

But the guessing game is over for now, and perhaps for the rest of the 1978 season.While Joe Theismann hardly earned selection to the All-Pro team, he performed well enough in Sunday's 16-14 upset of the New England Patriots to justify Pardee's faith in his skills.

Theismann, who completed 10 or 24 passes for 184 yards and a touchdown insisted he never really knew for sure he would start against the Patriots, that he simply assumed it. It is also safe to assume that Pardee will stay with him for all the same reasons that made him No. 1 against New England.

"From his preseason performances, the quarterback ratings, the opponent we were going to play, I though every factor indicated Joe should have a shot," Pardee said yesterday.

"One of the key things in the preseason was that in addition to not throwing any interceptions, he avoided getting sacked about 10 times.

"Going into that game, with New England's reputation, I thought he would have a better chance of avoiding those sacks and moving around a little better than Bill (Kilmer). Thankfully, he didn't have to run around too much. And with that knee coming up swelling, we didn't want him to."

So, for most of the afternoon, Theismann stood firmly in the pocket and allowed his offensive line to protect him against a New England defense that led the NFL in sacks the previous season.

Though he was smacked hard several times after releasing the ball, Theismann was sacked only once, a major factor in the Redskins starting victory. That same offensive line blocked well enough for the Redskins to gain 144 yards rushing, "and we should have had a lot more," Pardee said.

A John Riggins burst through the middle on a short-yardage situation late in the first quarter carried 43 yards, but was nullified when center Bob Kuziel was called for holding.

Pardee said Kuziel could hardly be faulted because the man opposite him submarined on the play. Kuziel fell on top of him and, Pardee said, "It's a questionable call, really. I don't know what else Bob could have done."

But Pardee was not about to accentuate the negative yesterday, not the day after one of the Redskins' most significant victories since they knocked off Dallas to gain a playoff berth in the final game of the 1976 season.

Pardee exulted over the performance of Coy Bacon, acquired in the offseason from Cincinnati. The 35-year-old defensive end made All-Protackle Leon Gray look like a Pop Warner League reject. Bacon was officially credit with two sacks, and harassed Patriot quarterback Steve Grogan all day.

Bacon apparently had been upset by a corny pregame show that featured a mild-mannered reporter walking into a telephone booth and emerging seconds later as Super Patriot.

"They were cocky," Bacon said. "You see a man in telephone booth jumping around like that, what else are you gonna think."

Pardee said linebacker Chris Hanburger had "one of the better games of his career." He added it was fitting that Dave Butz make the game's big play, forcing a Horace Ivory fumble that led to Brad Dusek's game-winning 31-yard touchdown run.

"Butz has worked hard, he had a good training camp," Pardee said. "I was glad to see him rewarded for it."

For the Redskins there were other significant rewards. They had come into the Patriot affair as nine-point underdogs, with All-Pro tight end Jean Fugett unable to play because of a bad knee. They also had undergone a tumultuous week that included the unpopular cuts of veterans Len Hauss, Rusty Tillman and Dennis Johnson.

There had been whispers of a morale problem among the team's older veterans. And in the final major practice of the week, Pardee became so upset with his offensive team that he kept it on the field an extra 25 minutes running plays.

So what did Sunday's victory mean?

"Well," said Pardee, "there were just so many great things that came out of the game. Everybody said the Redskins were an old team that hadn't played well on Astro Turf, playing a Super Bowl aspirant, playing on the road.

"Offensively, everybody felt we couldn't move the ball on the 3-4 defense and we accomplished that. That's important because we face another 3-4 this week and against St. Louis the next week.

"We got some confidence that whether it's a 3-4 or whatever front anybody uses, we can block it, we can run against it and we can pass protect and throw against, it too.

"For our young players, people making their first starts, like Kuziel, (Dan) Nugent, (Reggie) Haynes, even Joe, it was very meaningful. They had worked hard and all had good training camps. To have, their efforts rewarded with a win was awfully important."

Now the Redskins must take on an Eagle team that lost a heartbreaking decision to the Rams Sunday on a 46-yard field goal with 12 seconds left to play.

Pardee said he expects Fugett to be available, although he plans to continue to play Haynes, as well. Pardee also will use a little more of the 3-4 defense after staying mostly in the standard 4-3 against the Patriots.

"We were set to go either way against New England," Pardee said. "But after we were able to stop their running game pretty well in the first half, they started throwing play-action passes on first down.

"I knew with all their speed that we'd have to keep our pass-rushing group in there. I wanted to have four linemen in to rush the passer as much on first down as third down."

Though his wide receivers caught only five of the 24 passes Theismann threw Pardee said he had no major complaints with any of his players.

"There are things we have to correct in every phase of the game," he said.

"We also have 15 league games to go, and we can't get overconfident. But we play like that every week, we'll be all right."

Pardee may bring in several quarterbacks for tryouts this week. Jim Plunkett will not be among them . . . The Redskins had no injuries of major consequence . . . Eagle cornerback John Outlaw sprained a foot and may not be available . . . Pardee called the league for an interpretation of the illegal chuck [WORDS ILLEGIBLE] Parrish late in the fourth quarter and siad "I got one, but I didn't necessarily agree with it.

"When the quarterback is in the pocket, you can't jam (bump) the receiver," Pardee said. "Once the quarterback starts avoiding the rush or get out of the pocket, then the receivers lose all the protection. One of my complaints about the rule to begin with was that it was going to put a big burden on the officials making the call. How can they see [WORDS ILLEGIBLE] down field and also see where the quarterback is? Grogan was [WORD ILLEGIBLE] for his life, what was he, 12 or [WORDS ILLEGIBLE] behind the line? I don't exactly call that the pass pocket.Fortunately, the play didn't mean anything. But it really could have hurt us."