Tennis -- A chart in yesterday's editions mixed up winners of four Grand Slam tournaments in 1981. Martina Navratilova won the Australian Open, Hana Mandlikova the French Open, Chris Evert the Wimbledon and Tracy Austin the U.S. Open. (Published 9/12/90)

NEW YORK -- Pete Sampras is an unwitting U.S. Open champion. Just days ago he said he would not be ready to win a major title for another two years, a 19-year-old admittedly lagging behind fellow young Americans Andre Agassi and Michael Chang. Then he demonstrated a high-octane tennis game that may have more long-term possibilities than either of them.

When Sampras defeated Agassi in the men's singles final at the National Tennis Center Sunday, 6-4, 6-3, 6-2, he finally caught up. The son of a chemical engineer from Rancho Palos Verdes, Calif., already had leaped from No. 81 in the world to No. 12 with two singles titles this year. With his first Grand Slam victory he will attain the No. 6 position, a move almost as powerful as his 120-mph serve.

Sampras began the tournament as a potential-laden curiosity but served 100 aces to accomplish consecutive upsets of some of the most noted players in the world, including Ivan Lendl and John McEnroe. His straight-set victory over Agassi may have had significant implications for American tennis: The 20-year-old from Las Vegas who is ranked fourth was, until their final, considered Sampras's elder and superior. Now he must be considered a peer.

"It was the best I could possibly play," Sampras said. "The best all week and the best all year, and it couldn't have happened at a better time. I really don't know if anyone could have beaten me."

Not with a serve that regularly registered 100 mph, and sometimes ticked the lines of the service box at 124. Moreover, Sampras showed a smoothly elegant baseline game, and cobra-like volleying. That combination has in the last 24 hours drawn comparisons to Bill Tilden, the big serve-and-volleyer who made the U.S. Open finals eight consecutive years, tied with Lendl for the record. It also convinced Sampras that he was entitled to his first Grand Slam victory, something he did not believe at the outset.

"I would have said you were pretty crazy," he said. "But I think I deserved it."

Sampras's performance was the unexpectedly early culmination of several years of work. It began with his transition from a pouty, two-fisted baseliner going nowhere as a 14-year-old junior growing up in the same home town as Tracy Austin. Unhappy with his progress, he went to a one-handed backhand and began attacking the net.

"I wasn't improving," Sampras said. "I had a weak serve and I couldn't volley at all. I was very emotional, I was a counterpuncher. Then I switched to a one-handed backhand and completely changed every aspect of my game."

Sampras's game now revolves almost wholly around a serve that evoked more comment than any single stroke by any player in the tournament. "His serve is very big and very important," McEnroe said.

His serve is a reared-back delivery patterned after Rod Laver's, a smooth rock back on his heels and a large rotaton of shoulders and hips in concert that is not just lacerating but well-placed. He aced Agassi 13 times, with 12 more service winners.

"He's always had a big serve, but he put together some really exceptional placement the last couple of weeks," Agassi said. "You'd see all his aces are on the line. That's just tough. The chances of returning a serve that's hit 100 miles an hour on the line are slim, not to mention when he can blast one 120."

That makes Sampras different from the hordes of baselining American hopes such as 1989 French Open champion Chang, the 18-year-old currently No. 11 (and a victim of an early round upset by Andrei Cherkasov of the Soviet Union). Or Agassi or quarterfinalist Aaron Krickstein, who rely on jumped up force, high-tech, wide-body rackets and targeted placement.

Curiously, something similar happened among the women. Third-seeded Monica Seles was upset in the second round when she ran unexpectedly up against a serve-and-volleyer from Italy, Linda Ferrando. No. 5 Gabriela Sabatini of Argentina upset top-ranked Steffi Graf of West Germany in the final, 6-2, 7-6 (7-4), by changing her topspin, baseline tactics and charging the net. Graf chose to rely on her vicious power from the ground.

Graf failed to attack Sabatini's short, spinning second serve, and was tentative when she did venture in. That suggested that while Graf was secure in her ranking the past couple of seasons, merely consolidating her game, Sabatini was finding some alternative, staring at a 3-18 record against her rival and a ranking that went from No. 3 to No. 5. The result for the 20-year-old was a surge of improvement, the first Grand Slam title of her career and a move back to No. 4.

If Agassi learned one thing from the match with Sampras, it is that he must continue to improve. Long called a potential champion, he has been upset in two Grand Slam finals, losing the French Open to Andres Gomez of Ecuador this spring, because he lacked a confident, large attack.

Two statistics stood out when comparing Agassi to Sampras. Agassi relies heavily on his passive-aggressive game: His ability to return serve is crucial, and so are his passing shots. In the three tournaments he won this season, he broke his opponent's serve 51 percent of the time, and held to that through six matches at the Open. Against Sampras he failed, with just three break points in the match.

Sampras lost just 17 points in 13 service games. And there was another, bigger, even more appalling number to contemplate: For the tournament, of his first serves that went in, one out of every four was an ace.

Sampras's game was simply overwhelming, and without the inconsistency that has hampered him in the past. He lost in the round of 16 to Yannick Noah in straight sets at the Australian Open, and in the first round at Wimbledon to Christo van Rensburg, also in straight sets. But when he puts together a whole tournament, he draws raves. He defeated Gomez for his first pro title in Philadelphia in February.

"Probably, he's very underrated in America with the likes of Agassi and Chang," Gomez said after that match. "I have to say when asked 'Who's the best?' that Pete is. His game is complete, and I don't think Chang and Agassi will ever be serve-and-volleyers."

What remains to be seen about Sampras is whether he can maintain his current level. Serves are often temporary: No. 2 Boris Becker was beaten in the semifinals by Agassi when his booming delivery failed.

In Sampras's favor is a solid work ethic and good sense. His parents, father Sotorius (Sam) and mother Georgia, are retiring types who were too nervous to come to the Open or even watch on TV. Sampras was born in Potomac, Md., but moved to Rancho Palos Verdes as a child when his father decided to spend more time with the family. Sampras has traveled on his own for two years, accompanied only by Coach Joe Brandi. His parents are adamant in their refusal to shortchange his brother and two sisters. He does not have an entourage.

He has a thoroughly unaffected manner, and a strong, quirky sense of humor. Told the president might call him, he smiled with a shy grimace and said, "The phone's off the hook."

Asked to describe himself, he said, "I'm a normal 19-year-old with a very unusual job, doing very unusual things like I did today."