Leave it to Ilie Nastase, who always had a knack for combining exquisite tennis with burlesque, to perform the first known striptease in the history of the U.S. Open championships.

It came off shortly before 1 p.m. today, just behind the grandstand, the smaller (6,000 seats) of the twin arenas at the hub of the National Tennis Center in Flushing Meadow Park.

Not many people saw it because most of the matinee audience of 10,782 paying customers who attended the second day of the 13-day Open were otherwise engaged at the time -- watching John McEnroe pummel a hapless Czech named Pavel Slozil in the 19,000-seat main stadium, or sampling the smorgasbord of first-round matches set out on 13 spacious courts, or perhaps nibbling at another kind of sumptuous buffet in the tented pavilions hired for the day by Avon cosmetics and Miller beer for entertaining their clients and guests.

It was lunchtime, and so even just plain folks were seeking refreshments, perhaps frankfurters and sauerkraut (.90), quiche lorraine ($3.50), chocolate mousse cake ($1.95), or the other tempting goodies available to the public at the Open's varied concession stands, some of which are called "Courtside Cafes."

It was a very modest strip by contemporary community standards -- just a quick change of shorts by Nastase between games -- but somehow it seemed perfectly appropriate to this frenetic spectacle that interweaves sport, commercialism, corporate entertaining and show biz in a uniquely American way. Tournament director Bill Talbert calls the Open "a great fun carnival." Nastase calls it "the noisiest, craziest tournament I ever see."

Nastase is playing at Flushing Meadows, site of the 1939 and 1964 World Fairs and home of the Open starting last year, for the first time. A year ago he was absent, serving one of his several suspensions for misbehavior.

The "rambunctious Rumaniac" -- who won the Open in 1972, when it was played at the more staid West Side Tennis Club in nearby Forest Hills, and helped turn more than his share of tournaments around the world into unexpectedly noisy and crazy affairs -- is far past his prime at age 33, frequently an early loser nowadays. He is No. 24 in the current computerized world rankings, unseeded and seemingly incapable of winning big tournaments on sheer speed and genius with a racket as he did in the early 70s.

Nastase was leading Leo Palin, a less-than-flying Finn, 7-5, 6-5, but was getting restless. His long, lank locks were matted and dripping with perspiration in the clammy heat that turned into steady rain a couple of hours later, washing out most of the day's program. Planes taking off from LaGuardia Airport, half a mile west on Grand Central Parkway, were roaring overhead with deafening regularity. Nastase was having trouble keeping his mind on his match, which is hardly unusual.

At the change game, a reporter -- Mike Lupica of the New York Daily News -- walked along a chain link fence about 30 feet behind the court, heading for a seat in the stands behind the umpire's chair. Nastase spotted him and called out cheerily, "Lupica, how are you?" He picked up his folding chair, moved it to the fence, and launched into a conversation with the startled and vastly amused writer.

Earlier, Nastase had sent a young tournament employee to the dressing room to fetch him a dry pair of shorts. The youngster arrived and handed them to "Nasty," who stood up and raised his arms.

"Excuse me, everybody," Nastase said loudly, though relatively few spectators could see him. He dropped the sweat-soaked white shorts he had been wearing, kicked them away, giggled, and pulled on the blue ones. Of the half-dozen gawking photographers at courtside, none was quick enough to catch the fleeting shot of Nastase.

Then the erstwhile maestro went out and played, obviously pleased with his little bit of exhibitionism. The match lasted only one more game, Palin defaulting with a pulled leg muscle after losing the second set, 7-5.

Afterwards, Nastase went back to the dressing room and showed off a comic strip he has taped to his locker -- a "Tank McNamara" cartoon which shows a ticket booth featuring a sign that says, 'Nastase vs. McEnroe, 7:30 tonight" . . . and then another panel with the warning, "This match is rated R.No one under 17 admitted without parent or guardian." Nastase loved it, especially since he will play McEnroe in his next match here.

Someone asked him if it were possible in this day and age to play professional tennis seriously and still have fun.

"I do both. Is a good mix," Nastase said. He frowned and gestured around the players' lounge. "These guys don't have a good time," he said, launching into a lengthy criticism of the modern tennis pro as young businessman and mini conglomerate.

"They all have someone to carry the rackets, someone to carry the shoes, someone to carry the bag, someone to sign things. It will be like Hollywood pretty soon," he said.

"Little girls who can't play at all, they have coaches. They bring their mother and father and sister. You can't move around this lounge. And nobody has fun."

After a shower, Nastase went to the interview room where perhaps two dozen media types were waiting to talk to him. "A lot of ladies here, so I leave my pants on," he said, grinning like a canary that swallowed a cat. He looked straight at one woman reporter. "You want my pants on or off?"

He was asked if the conditions at the Open -- particularly the noise level -- bothered him.

"You can't do anything about noise. You can just play, and the planes still go over," he said. "They have to take off every day, so what can you do? People have to go home.

"But I guess if you want to win the U.S. Open, you have to take the noise, you have to take everything. That's why Borg and Connors are great. They can do it. They can concentrate for two weeks. I cannot do that. I don't think many players can do that. It's very difficult, you know."

McEnroe, who is seeded third behind Bjorn Borg and Jimmy Connors in the Open, had been in the same seat a few minutes before. He has a reputation for having rabbit ears, and was accused by an opponent earlier this year of having "missed his calling -- as an usher," but today he said players simply have to accept the distracting noise and bustle of the Open. "Those are the conditions, and you have to perform," he said.

Of his second-round opponent, Nastase, McEnroe said: "He was a great player, but I don't think he's a great player now . . . I'm sure he's going to try and bug me, so it should be interesting to watch . . . It's funny to watch him, but it's not funny for the player playing him."

Informed of the young left-hander's remarks, Nastase smiled. His eyes twinkled with mischief. "He said that? For sure, yeah, I bug him," he said. "If he says that, it bothers him. I can see it bothers him. I think I bug anybody, not especially John.

"Don't put this in the paper, but I like him. Don't say that, because I never told him that," Nastase added later. "I enjoy McEnroe because his game is so complete. He can play hard, play soft, play anything. I like to watch him more than anybody else because he can play topspin, slice, everything, and he hits crazy shots too, which is the kind of game I play."

Finally, someone asked Nastase why he had changed his pants in public -- or at least, semipublic.

"It was so heavy out there, I just go under the stadium and I change. What's wrong? Everybody else is hanging their shirt, so I change my shorts. I don't want to be like everybody else," he said.

Not much chance of that.

"All the guys are sweating up here," Nastase added, sweeping his hand across his shirt, "But I have a big butt.I sweat in the butt. So I say to everybody, "I'm sorry, I change my pants, do you mind?' The ladies say, 'No, go ahead.'"

Tank McNamara obviously knew whereof he spoke, and that is why not many people will be lunching or drinking or wandering the grounds when Nastase plays McEnroe.

They will flock from the brightly striped tents and the outside courts and the "courtside cafes" into the stadium, with its steeply-banked red, white and blue seats and ornamental plastic geraniums, to watch the young hotshot play tennis's authentic "wild and crazy guy."