NEW YORK, AUG. 30 -- There was a somnolence at the U.S. Open today that made you want to curl up in a bleacher and take a nap, but trust Andre Agassi to wake up the place. The victories came in straight, routine sets, with hardly a cloud in the sky or an upset in the field at the National Tennis Center, until Agassi took the court tonight with his loud clothing and mouth.

The matches had a lulling quality, exemplified by defending champion Boris Becker's victory over Yannick Noah, 6-4, 6-2, 7-6 (7-2), to move with surprising ease into the third round. Then came the 20-year-old, Las Vegas light bulb, Agassi, whose taut four-set victory over Petr Korda, 7-5, 5-7, 6-0, 6-4, included obscenities and an ugly spitting incident with the chair umpire.

Agassi's encounter with Wayne McKewen occurred as Korda served in the 11th game of the second set. McKewen overruled a line call at deuce, giving Korda game point. Agassi then drew a warning for an audible obscenity directed at McKewen. Korda went on to hold serve, and on the changeover Agassi spit, apparently at McKewen. The umpire immediately gave Agassi a point penalty and called for tournament referee Keith Johnson and Grand Slam supervisor Ken Farrar.

Johnson and Farrar told McKewen to rescind the penalty, because "he may have misread" the gesture. But McKewen misunderstood and assessed it anyway, which meant that Agassi would be another violation from disqualification. Agassi erupted, Johnson and Farrar returned, and finally it was settled with no penalty. McKewen rolled his eyes, and the match continued.

Later, Agassi denied he used obscenities, but admitted that some of his saliva hit McKewen. "I didn't swear," he said. "I spit, but not at him. Obviously some of it hit him, but it wasn't intentional. The referee used his best judgment and said no way I meant it." Agassi also said he apologized to McKewen afterward.

"I got carried away with the fact that there were a few bad line calls," he said. "I think there are a lot more positive things to talk about. I yelled out in anger and he saw it as abusive language. He thought I swore, which I didn't. Then I lost my temper."

It was the only real event of the second round, in which several promising matches failed to materialize. No. 11 Michael Chang met Jimmy Arias in a match between past and future: Everything 26-year-old Arias was once supposed to be, 18-year-old Chang has become. The idea was romantic enough, but the reality was suspenseless, an emphatic victory for Chang, 7-6 (7-3), 6-3, 6-2.

The only upset of note was Gary Muller besting No. 14 Jim Courier, 4-6, 6-4, 7-6 (8-6), 7-6 (7-5). And even that wasn't so surprising, since Muller, ranked No. 61, has beaten Brad Gilbert and Stefan Edberg this season, and has a massive serve that worked for 24 aces today.

Eight of the nine women's seeds who embarked on second-round play today came through in straight sets. No. 1 Steffi Graf defeated Rachel McQuillan, 6-3, 6-1; No. 3 Monica Seles opened play on Stadium Court, easing past Ros Fairbank-Nideffer, 6-2, 6-2; No. 4 Zina Garrison recovered from a stream of 25 errors in the first set for a 6-4, 6-0 victory over Angelica Gavaldon; and No. 13 Jennifer Capriati started sleepily against Patricia Hy, but eventually routed her, 6-3, 6-1.

Among the men, No. 15 Goran Ivanisevic relied on 11 aces to counter his 28 unforced errors, and overcome Jean-Phillipe Fleurian and a third-set bout with inattentiveness, 6-4, 6-2, 3-6, 6-1. No. 9 Aaron Krickstein downed Jason Stoltenberg, 6-4, 6-2, 6-4, while No. 8 Gilbert withstood a shaky start against doubles specialist Rick Leach, 7-6 (7-4), 6-4, 6-2.

Noah threatened to extend Becker in the taut third set when he broke serve for 5-3. But the moody, expressive Frenchman allowed Becker to break back, aiding him with a double fault. He was a non-factor in the tiebreaker.

That summarized Noah's problems lately. His game is still elegant but increasingly fragile, the 1983 French Open champion now ranked No. 35. He also had little with which to combat Becker's pure force, the West German battering him with 43 winners. Noah had just 16, and won only three points off Becker's serve in the landslide second set. "It felt terrible," he said.

Noah, now 2-3 against Becker, has not beaten the West German since 1988, and suffered a similar straight-set loss to him in last year's Open quarterfinals. His best performance of the season is a semifinal appearance in the Australian Open, but he also has lost in the first round nine times in 16 tournaments.

Noah appears confused and distracted, at times working feverishly with coach Dennis Ralston and at others preferring to spend time on his sailboat or with his family. He is contemplating a sabbatical, but admitted that if he did leave the game now it would probably be for good.

"It's a difficult situation where I am not playing well and I'm getting really frustrated," Noah said. "I'm interested in other things besides tennis. After every tournament I am thinking, 'Okay, what's next?' I'm just living one week after the other right now."

Chang and Arias represented eerie reflections of each other. In 1983 Arias was an 18-year-old sensation who won the Italian Open. In 1989 Chang won the French Open at 17. Arias was a U.S. Open semifinalist in '84, but since has not reached even the quarterfinals of a Grand Slam event, plagued by injuries. Chang fractured his hip in December.

It will be interesting to see if Chang can avoid future comparisions to Arias, and the burnout and ailments that seem to strike younger players.

"Young players can learn to take better care of their bodies, I think," Chang said. "I learned that recently. The tour is very demanding, not only on your body, but on your mind, You have to be ready physically in order to deal with that."

With all the anticipated confrontations turned into routs, the best matches of the day instead came in doubles competition. John McEnroe and Mark Woodforde fell in the first round to No. 7 Guy Forget and Jakob Hlasek in straight but thrilling tiebreaker sets, 7-6 (8-6), 7-6 (8-6). Second-seeded Martina Navratilova and Gigi Fernandez were extended by impudent teenagers Capriati and Meredith McGrath, 7-5, 6-4.