PARIS, MAY 31 -- Defending women's champion Arantxa Sanchez Vicario was the victim of another historic upset at the French Open today, beaten in the second round by Mercedes Paz, her doubles partner.

Second-seeded Monica Seles almost joined No. 3 Sanchez Vicario on the sidelines. The 16-year-old dropped her first set in 2 1/2 months, then rallied for her 27th consecutive victory, 4-6, 6-4, 6-4 over Helen Kelesi.

Thirty-ninth-ranked Paz, who has spent most of her career in the shadow of fellow Argentine Gabriela Sabatini, ran down the Spaniard's varied shots to win by 7-5, 3-6, 6-1, breaking into tears of joy over her biggest victory.

"I feel very, very happy," said Paz, who lives in Key Biscayne, Fla. "It was a dream to play on center court and to beat the champion of last year."

It was the earliest a defending women's champion had gone out of the Grand Slam tournament, according to the Women's International Tennis Association. The previous record was the third round, when Margaret Court fell to Gail Chanfreau in 1971.

"What can you do? Tennis is like that," Sanchez Vicario said. "She played better than me and that's why I lost today. . . . I won last year; this year is like this. I'll try again next year."

It was a sloppy match, with nine service breaks in the first 12 games, both players making a slew of errors. But Paz was steadier on the big points, especially in the third set, and Sanchez Vicario never found the magic that helped her upset Steffi Graf in last year's final.

"She was very nervous and never knew what to do," Paz said. "In the third set, I think she got tired and felt the pressure more. My tactic was to move her and hit the ball hard."

Men's fifth seed Aaron Krickstein won handily, as did Jennifer Capriati, who took just 40 minutes to beat Cammy MacGregor. But 12th-seeded Juan Aguilera was upset by Frenchman Thierry Champion, much to the delight of the crowd at Roland Garros.

But the opening match on Court Central provided another huge jolt to a tournament that was just getting over Tuesday's upsets of men's top seeds Stefan Edberg and Boris Becker, the first time Nos. 1 and 2 have been beaten in the first round of a Grand Slam event.

Sanchez Vicario helped beat herself. Drop shots and volleys that found the corners and lines a year ago landed long and wide today, and Paz, winner of a French warm-up in Strasbourg, France, was good enough to capitalize.

"I feel like all the hard work has paid off," she said.

Paz needed four set points in first set. Sanchez Vicario saved two of them to pull to 5-5 and got a third back in the 12th game before Paz wrapped it up.

Sanchez Vicario appeared to take the momentum in the second set, going up by 5-1 before Paz won two games in a row, saving a set point in the eighth. The Spaniard held serve to close out the set.

Still, Paz was pumped up, shaking her fist as she won the opening game of the final set. That was the first of four in a row, and Sanchez Vicario folded meekly after winning the first two points on Paz's serve in the final game. Paz hit a forehand volley winner, then let two Sanchez Vicario errors move her to match point.

When Sanchez Vicario sent a forehand long, Paz dropped her racket at the baseline, raised her arms and broke into a big smile. She ran to the net, where she and Sanchez Vicario exchanged kisses and hugs, then walked to her chair, sat down and sobbed with joy.

"I felt a little sad for her because I knew how she must feel to lose in the second round," Paz said. "But I am happy for me to be the one to beat her."

Seles came into the tournament as the hottest player in tennis, having just beaten top-ranked Graf. She hadn't dropped a set since losing to Laura Gildemeister at the International Players Championships in March, but Kelesi stopped that streak in the first set.

In the seventh game of the second set, Kelesi saved a break point and had a point to hold for 4-3 when Seles floated a drop shot for deuce. She then got the crucial break on two Kelesi errors and finished the set with another drop-shot winner.

It was one set later when the hard-hitting Seles again turned to touch to break Kelesi. At 15-40, Seles charged a soft second serve and hit a drop-shot return to break. On match point, Kelesi tried to use the same trick. She dumped a drop shot, but Seles ran it down and scooped it back. Kelesi had an open court to send the game to deuce, but netted the volley, ending the match.

"It was only a question of a few points," Seles said. "There was a permanent tension in the match. I'm happy it's finished."

Among other women's seeds, No. 6 Manuela Maleeva beat Anne Minter, 6-1, 6-0; No. 16 Gildemeister downed Elise Burgin, 6-3, 6-4; and No. 10 Natalia Zvereva eliminated Iva Budarova, 6-1, 6-3.

Capriati beat MacGregor, 6-1, 6-0, pushing her record since turning pro to 18-4 and her Grand Slam mark to 2-0. "I don't feel pressure, I'm glad to be playing here," she said.

Krickstein beat Stephane Grenier, 6-3, 6-4, 7-5, to reach the third round here for the first time since 1987. Champion beat Aguilera, a clay-court specialist considered among the favorites, 3-6, 6-3, 6-3, 6-2.

Graf pulled out of the doubles today. She said Wednesday after her second-round singles victory that she was bothered by sinus problems apparently caused by an allergy. She won her won her first two singles matches in straight sets.

Graf and teammate Sabatini withdrew before their first-round match and were replaced in the draw by Andrea Vieira and Pilar Vasquez. TODAY'S FEATURED MATCHES Court Central

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Jordi Arrese, Spain, vs. Andrei Chesnokov (8), Soviet Union; Gabriela Sabatini (4), Argentina, vs. Nathalie Herreman, France; Andre Agassi (3), Las Vegas, vs. Arnaud Boetsch, France; Julie Halard, France, vs. Katerina Maleeva (8), Bulgaria. Court 2

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Johan Anderson, Australia, vs. Jim Courier (13), Dade City, Fla.