NEW YORK, SEPT. 3 -- Steffi Graf drove Jennifer Capriati to a sugar binge, the 14-year-old wolfing brownies, swigging ginger ale, sucking on a lollipop and chewing gum at the same time. Boris Becker berated himself with all the ugly words he could think of before he defeated Darren Cahill over five sets. Those were the varied ways defending champions Graf and Becker put down upset threats at the U.S. Open today to reach the quarterfinals.

There is something irresistible about a match between Graf, the grim former child star, and Capriati, the current Shirley Temple of tennis. But as so often happens when expectations are heaped on an occasion, this one did not meet them. Graf dismissed Capriati, 6-1, 6-2, in the fourth round at the National Tennis Center to wipe the grin off the Florida teenager's face. Capriati sprayed errors around the court in a disappointing exhibit of nerves, and then did what 14-year-olds do: She stuffed a wad of gum in her mouth.

"It's not the end of the world," she said.

Becker knew he would have difficulty with Cahill, a hard-faced Australian who had upset him in the second round of the 1988 U.S. Open over five sets, and eventually made the semifinals. Cahill harassed him with jab-like volleys and rolling passing shots for three hours 14 minutes before Becker finally emerged, relieved and not without a few fits of temper, 2-6, 6-2, 6-3, 3-6, 6-4. He celebrated by throwing a stack of shirts into the stands.

"I found a way, talking to myself, loudly," Becker said. "Mixed up, all the words I know in any language."

So for one day, there were no upsets at the Open. That was an upset in itself, since the tournament has been plagued by them. With their victories, Graf and Becker had to be encouraged about the chances of defending their titles, their paths cleared by the startling losses of several seeded players and rivals. Top-ranked Stefan Edberg lost in the first round, and Becker has no one higher than No. 4 Andre Agassi left in his half of the draw. They would meet in the semifinals.

In the quarterfinals Becker will play No. 9 Aaron Krickstein, who beat Amos Mansdorf, 6-3, 6-4, 6-4.

Agassi, the 20-year-old from Las Vegas with the neon clothes, defeated No. 13 Jay Berger, 7-5, 6-0, 6-2, in 1 hour 50 minutes. He then created a near riot by throwing his chartreuse and black mesh shirt in the stands. His next opponent will be Andrei Cherkasov of the Soviet Union -- the upsetter of 11th-seeded, former French Open champion Michael Chang -- who today defeated South African Christo van Rensburg in straight sets.

The attrition rate among the women has been lower, but those who have fallen have been significant. When No. 2 Martina Naratilova was beaten in the fourth round by No. 9 Manuela Maleeva-Fragniere and No. 3 Monica Seles was stunned by unseeded Linda Ferrando of Italy in the third round, it marked the first time in the era of open, professional tennis that dates from 1968, that the second and third women's seeds failed to reach the quarterfinals.

But that doesn't necessarily guarantee Graf's entry in the final. With her victory she arranged a quarterfinal meeting with dangerous 12th-seeded serve and volleyer Jana Novotna of Czechoslovakia, who advanced today by upsetting No. 7 Katerina Maleeva of Bulgaria, 6-4, 6-2. She then has a potential semifinal meeting with fourth-seeded Zina Garrison, the 26-year-old who is playing the finest tennis of her career.

Garrison defeated Nathalie Tauziat of France, 6-1, 7-5, a surprisingly easy progress to the quarterfinals against a player who had extended her to three sets in several previous meetings this season. Garrison's performance today proved her form has not diminished since Wimbledon, where she upset Graf in three sets to reach the first Grand Slam final of her career, only to lose to Navratilova.

Garrison and Graf are now headed towards another semifinal, but first Garrison must meet sixth-seeded Arantxa Sanchez Vicario of Spain, the 1988 French Open champion, who defeated No. 16 Barbara Paulus, 6-4, 6-3. Garrison has not received the attention she should have here, but that's fine as far as she is concerned: that is how she surprised Graf at Wimbledon.

"That's the way I like it," she said. "You sneak up on them before they know it. It's happened a whole lot and I don't really worry about it. It's much easier to concentrate that way, and you just go on and play tennis."

Lack of concentration has been Graf's downfall this season, with the 21-year-old plagued by a variety of health problems such as a sinus condition during Wimbledon and a stomach ailment earlier this week. She was apprehensive about her third career meeting with Capriati; although she beat the Florida teenager convincingly in the fourth round of Wimbledon, 6-2, 6-4, she was extended to three sets at an exhibition in Mahwah, N.J., the week before the Open, 6-3, 5-7, 6-4.

Capriati might have made it a close match today had she been able to break Graf in either the sixth or eighth games of the second set, wasting three break point opportunities. "I thought maybe I could hang in there," she said. She could not. The rest was a sweep by the West German, who broke Capriati for 5-2, and fended off a break point set up by her double fault in the last game before she tore into a savage goodbye forehand on match point.

"If you don't lose, then you can't learn anything," Capriati said. "I wasn't making the shots. Next time, I can't let that happen."

Capriati could console herself with candy and the knowledge that there surely will be a next time. As for Graf, it was her most dangerous match thus far, and she came out of it reassured. Still, she is not yet content with her sometimes loose play, the slipshodiness that cost her the French Open against Seles, and the Wimbledon semifinal against Garrison. "It's getting better," she said.

Becker also is getting better. The 23-year-old has a method in Grand Slam events, preferring to build his form gradually, and he doesn't mind having to "dodge a bullet" in an early round, as he puts it. While that makes him prone to upset, it also helps him peak, and Cahill may have done him a favor today. "I hope this was it," Becker said.

He struggled early to find the rhythm on his massive serve, and Cahill took the first set in just 29 minutes. That worried the West German only briefly, sweeping the next two sets almost as quickly. But Cahill, although he is ranked just No. 48, is an indefatigable player who outlasted Goran Ivanisevic of Yugoslavia in five sets to reach the fourth round, and he constantly took Becker aback with his winners, 52 of them.

Cahill broke Becker consecutively for a 3-0 lead to open the fourth, chiefly by staying in points when Becker thought they were over. On break point in the third, he raced to retrieve Becker's net-cord forehand and drilled it down the line. Becker lunged for a backhand volley that he sent into the net.

The West German could not make up the deficit as Cahill fought off four break points in the sixth game and two in the eighth. Cahill broke Becker yet again for the set, when the West German stood flatfooted as a backhand slice return appeared to be going out, but suddenly dropped in. Becker stared at the baseline, and they went into the fifth set.

Becker likes to say that fifth sets are more a matter of character than tennis. That is what happened, as he took the match with one crucial service break in the seventh game.

"I thought I was playing well the whole match, and it was just a matter of winning a couple of points here and there," Cahill said. "I was confident, but he played the bigger points better than I did."

Becker created break point with a wrenching backhand pass down the line, then nailed a forehand at Cahill that the Australian mishandled with a forehand volley to fall behind, 2-4. Cahill did not get so much as a break point against Becker, who closed it out with a series of high kicking service winners the Australian could only block into the net.

"You're always better if you come through" a five-setter, Becker said. " . . . I had to find a way, I was trying to find a way and I finally did it."