NEW YORK, SEPT. 1 -- Steffi Graf went for a walk in the third round at the National Tennis Center today, but at least she came back. Goran Ivanisevic went in the tank.

Ivanisevic, an 18-year-old Yugoslavian, is projected as the next great player. But he openly admitted to throwing away the fifth set after losing a two-set lead against unseeded Darren Cahill of Australia, 4-6, 4-6, 6-2, 7-6 (7-3), 6-0. He won four points in the final set.

"I went crazy, I don't know," Ivanisevic said. "In the fifth set to give up, it's crazy. I don't know what happened in my mind."

Cahill's dubious victory ruled out what would have been one of the most compelling matches of the tournament, a fourth-round meeting between Ivanisevic and defending champion Boris Becker. Ivanisevic upset Becker in the first round of the French Open and nearly upset him again in the Wimbledon semifinals. He earned his first seed in a Grand Slam event here on the basis of those results and his obvious talent. He has one of the hardest serves and most powerful ground strokes in the game, skills that have evoked comparisons to Becker.

But if Ivanisevic is going to rise to Becker's stature he must cure his emotional problems. He lost his composure against Cahill at 3-3 in the third set after he failed to break the Australian's serve despite a 0-40 lead. Cahill unleashed four straight first serves to hold, and Ivanisevic gave him the set.

"I tank two games," he said.

Ivanisevic tried earnestly in the fourth set, but he lost control of his emotions again early in the tiebreaker, double-faulting on the second point to give Cahill a mini-break the Australian never relinquished. He then failed to show the slightest effort beyond the second game of the fifth set, when Cahill held serve for a 2-0 lead.

"It was a gutless effort," Cahill said. "I don't know what makes a man do that. You'd have to ask him what he was thinking at that stage. I'm out there to win, trying to keep the ball in play, and he was handing it to me. I'll take it how I can get it."

Ivanisevic merely spun his serve into the court over the last four games of the match. Of his 11 aces, seven came in the fourth, none in the fifth.

"I loved it," Cahill said.

Ivanisevic left the court close to tears, and to a rising chorus of boos.

"I don't care," he said. "But maybe they're right."

Ivanisevic's saving graces are a friendly, open nature and acute honesty. His composure regained an hour later, he discussed his behavior at length, clearly abashed. He said he has given away sets before, inspiring lectures from his coach, Balazs Taroczy. "Don't tank," Taroczy told him severely at the French Open.

Ivanisevic admitted giving away the third set here in the second round against Jean-Phillippe Fleurian of France before recovering for a four-set victory. But he said he had never relinquished a fifth set this way.

"After 2-0, it was tanking," he said. "I'm not trying, and I just want to finish the match. I don't know why really. The fourth set, to play two hours, I sweat a lot. In the fifth set to give up, it's crazy.

"I hope I learn something and don't do it again. I'm sad because I lost this match very stupid. If I learn something from this match, okay. If not, then it's not okay."

Grand Slam supervisor Ken Farrar, after a discussion with Ivanisevic, declined to fine him. "This is a young man who is 18 years old and and speaks broken English and misconstrued the use of the term 'tank,' " Farrar said in a statement. " . . . What he intended to say was that, after the second game in the fifth set, he was mentally beaten . . . ."

Ivanisevic's loss doesn't mean Becker has a walkover to the quarterfinals. The West German defending champion tonight advanced past No. 84 Thomas Carbonell of Spain, 6-4, 6-2, 6-2, but in the fourth round he has something to fear from Cahill, who upset him here in 1988 and reached the semifinals.

Ivanisevic's loss was only the second- or third-largest upset of the day, but its circumstances overshadowed the others. No. 8 Brad Gilbert also lost a two-set lead, succumbing to unseeded, No. 41-ranked Amos Mansdorf after five sets and 4 hours 5 minutes, 5-7, 5-7, 6-3, 7-5, 6-1. No. 11 Michael Chang, 1989 French Open champion, was defeated by No. 50 Andrei Cherkasov of the Soviet Union, 6-4, 6-4, 6-3.

Gilbert's loss was not as startling as it seemed, considering his history of poor performances in Grand Slam events. Last season he did not win a match in the Australian, French or U.S. opens or Wimbledon, despite a No. 4 ranking. Mansdorf has frequent success against him, their career series tied at 4.

Chang killed three match points before he yielded, but he was lacking his usual stubborness. He has come back from two-set deficits four times and has a 6-1 career record in five-set matches, but Cherkasov did not allow him any breathing room. The Soviet player beat Chang at his own baseline, counterpunching game, outlasting him in a duel that lasted 2 hours 41 minutes, for all that it was straight sets.

"I had trouble staying with him," Chang said. "A lot of times I'd just miss. Or he'd come back with a better counterpunching shot."

Even the victories did not come easily. No. 9 Aaron Krickstein survived a dangerous third-round opponent in former Wimbledon champion Pat Cash, who has not yet recovered from a torn Achilles' tendon that sidelined him for a year. Krickstein's straight-set victory was closer than the score, 6-4, 7-6 (7-4), 7-6 (7-2), and took 2 1/2 hours. No. 13 Jay Berger recovered from a two-set deficit to defeat unseeded Cristiano Caratti of Italy, 4-6, 2-6, 6-4, 6-3, 6-4.

"I think in this day and age there are so many good players that it's dfficult to go out and beat everybody comfortably," Chang said. "That's why there are so many upsets. You have to just take them as they come. You win some, you lose some."

Ivanisevic's scandalous behavior rivaled that of Andre Agassi as the most controversial of the tournament. Agassi, fined $3,000 by Farrar for unsportsmanlike conduct, obscene language and spitting at a chair umpire in his second-round match with Petr Korda of Czechoslovakia, was on good behavior as he breezed past Franco Davin of Argentina, 7-5, 6-4, 6-0.

It is not often that top-ranked Graf lets an opponent affect her the way Elna Reinach of South Africa did this afternoon. Graf led by a set and a service break when she suddenly vaporized, letting Reinach tie their third-round match at a set apiece. She materialized again to move into the round of 16 with a 6-4, 3-6, 6-1 victory, but not without raising some doubts about her form.

Of the eight women's seeds who completed third-round play today, only Graf and No. 10 Conchita Martinez of Spain failed to advance in straight sets. Martinez was upset by Nathalie Tauziat of France, 6-2, 6-1. As for Graf, it appears the once invincible player who won the Grand Slam in 1988 is at 21 a chased and less feared opponent. Graf had won her two previous meetings with Reinach in straight sets, dropping no more than four games.

"They've seen me, they've played me, they know what to expect," Graf said. "They're not so afraid of me anymore."

Graf's difficulty was partly due to Reinach's array of junk shots -- low, twisting slices on which Graf could not exert her notorious pace.

Graf, with 34 errors, must lower that considerably against Jennifer Capriati. The teenager defeated Maria Strandlund of Sweden, 6-1, 6-4, to set up their meeting and has shown no sign of skittishness in her Open debut. "I'm very eager, I'm psyched," Capriati said. " . . . If you're not going to think you can get close, what's the point? You have to think you can beat her."


Boris Becker (2), West Germany, def. Tomas Carbonell, Spain, 6-4, 6-2, 6-2; Andre Agassi (4), Las Vegas, def. Franco Davin, Argentina, 7-5, 6-4, 6-0; Amos Mansdorf, Israel, def. Brad Gilbert (8), Oakland, 5-7, 5-7, 6-3, 7-5, 6-1; Aaron Krickstein (9), Grosse Pointe, Mich., def. Pat Cash, Australia, 6-4, 7-6 (7-4), 7-6 (7-2); Andrei Cherkasov, Soviet Union, def. Michael Chang, Placentia (11), Calif., 6-4, 6-4, 6-3; Jay Berger (13), Weston, Fla., def. Cristiano Caratti, Italy, 4-6, 2-6, 6-4, 6-3, 6-4; Darren Cahill, Australia, def. Goran Ivanisevic (15), Yugoslavia, 4-6, 4-6, 6-2, 7-6 (7-3), 6-0. WOMEN'S THIRD ROUND

Steffi Graf (1), West Germany, def. Elna Reinach, South Africa, 6-4, 3-6, 6-1; Zina Garrison (4), Houston, def. Silke Meier, West Germany, 6-4, 6-3; Arantxa Sanchez Vicario (6), Spain, def. Patty Fendick, Sacramento, Calif., 6-2, 6-1; Katerina Maleeva (7), Bulgaria, def. Raffaella Reggi, Italy, 6-4, 6-0; Nathalie Tauziet, France, def. Conchita Martinez (10), Spain, 6-2, 6-1; Jana Novotna (12), Czechoslovakia, def. Laura Gildemeister, Peru, 6-3, 6-1; Jennifer Capriati (13), Broken Sound, Fla., def. Maria Strandlund, Sweden, 6-1, 6-4; Barbara Paulus (16), Austria, def. Ann Grossman, Grove City, Ohio, 6-4, 6-3.TODAY'S FEATURED MATCHES Stadium Court

Ivan Lendl (3), Greenwich, Conn, vs. Gilad Bloom, Israel, 11 a.m.; Emilio Sanchez (7), Spain, vs. John McEnroe, Cove Neck, N.Y.; Martina Navratilova (2), Aspen, Colo., vs. Manuela Maleeva-Fragniere, Switzerland; Thomas Muster (6), Austria, vs. Pete Sampras (12), Palos Verdes, Calif., 7:30 p.m. Grandstand Court

Mary Joe Fernandez (8) Miami, vs. Judith Wiesner (15), Austria., 11 a.m.; Gabriela Sabatini (5), Argentina, vs. Helena Sukova (11), Czechoslovakia; Kevin Curren, Austin, Tex., vs. David Wheaton, Excelsior, Minn., 7:30 p.m.