PARIS, JUNE 4 -- Streaks and slumps were the focus of the French Open today as Monica Seles won her 29th straight match to reach the quarterfinals and Gabriela Sabatini endured yet another Grand Slam failure.

In the men's field, Americans Andre Agassi and Michael Chang were left as the only seeded players in the top half of the draw as No. 8 Andrei Chesnokov and No. 15 Guillermo Perez-Roldan were upset.

After trailing by 1-4 in the first set, the second-seeded Seles won 11 games in a row to beat Laura Gildemeister of Peru, 6-4, 6-0. Gildemeister was the last to beat Seles -- nearly three months ago in the round of 16 at the Virgina Slims of Florida.

Sabatini won that tournament but has since faded. And today the fourth-seeded Argentine was ousted, 6-4, 7-5, by No. 11 Jana Novotna of Czechoslovakia, marking the second year in a row she has lost in the fourth round here at Roland Garros.

In the men's fourth round, French wild card Henri Leconte thrilled the center-court crowd by beating Chesnokov, 6-4, 6-3, 4-6, 2-6, 6-3. Unseeded Jonas Svensson of Sweden, a semifinalist here two years ago, downed Perez-Roldan, 2-6, 6-4, 6-2, 6-2.

Leconte and Svensson will meet Tuesday in one quarterfinal in the top half of the draw. The other quarterfinal will match the third-seeded Agassi and Chang, who is defending champion and 11th seed.

In the bottom half of the men's draw, seventh-seeded Thomas Muster of Austria and unseeded Goran Ivanisevic of Yugoslavia reached the quarterfinals today, along with France's Thierry Champion -- the first qualifer to reach the quarterfinals in the Open era.

Muster, one of the hottest clay-court players on the men's tour this spring, beat No. 10 Martin Jaite of Argentina, 7-6 (7-4), 6-3, 6-2. Ivanisevic, who eliminated Boris Becker in the first round, swept past Niclas Kroon of Sweden, 6-2, 6-4, 7-5. Champion saved two points in the fourth set and beat Czechoslovakia's Karel Novacek, 6-3, 4-6, 3-6, 7-6 (7-5), 6-3.

Today underlined the contrasting fortunes of the 16-year-old Seles and Sabatini.

Seles has won five straight titles, including wins over Martina Navratilova and Steffi Graf in her last two tournaments. But she has been flat in her early matches in Paris, and she fell behind early against Gildemeister. While Seles had trouble keeping her shots in the court, the Peruvian moved her around with crisp groundstrokes and raced to a 4-1 lead.

"I wasn't into the match the first couple of games," Seles said. "I was missing balls I usually never do. I felt a little paralyzed."

Finding the range with her two-fisted ground strokes, Seles reeled off five games for the set, then won the second set at love in 16 minutes. She won 32 of the last 38 points, losing just four points in the second set.

Yet Seles was not completely satisfied.

"I just haven't been playing as well as the last couple of weeks," she said. "I think beating Martina and Steffi in a row really took it out of me mentally. I just gave everything in those two tournaments. But it's now the second week and I think my game is going to come back."

Novotna, a quarterfinalist here last year, took big leads in both sets as she kept Sabatini at bay with a strong forehand and a slice backhand. The Czechoslovak survived a scare when, leading by 2-0 in the second set, she twisted her right ankle stretching for a shot.

"I said to myself, 'This can't be possible. I've been playing so well and now I'm going to get injured,' " Novotna said.

But when her ankle was taped, she was back in business. Novotna broke serve for 3-0 and moved out to a 5-1 lead. Sabatini saved two match points in the seventh game and won the next three games to even the set at 5.

Novotna said: "At 5-1, I thought, 'It's okay. If I don't do it now I can do it later.' But Sabatini started playing much better and suddenly it was 5-all."

Novotna broke for 6-5 with a forehand cross-court passing shot and served out the match in the next game.

"I didn't feel very comfortable today," Sabatini said. "I was hitting the ball late from the beginning. I think it was just a bad day today. I shouldn't lose to her. It was a very big upset. I thought I was going to do really well in this tournament."

Leconte, the French left-hander with the aggressive all-court game, ran his record to 6-0 against Chesnokov. After winning the first two sets, his go-for-broke style took its toll. Many of the shots that were hitting the lines were now sailing out.

Chesnokov, a clay-court expert who was considered a strong contender for the title, played his patient baseline game to even the match at two sets apiece.

Leconte had been in the same situation before. He had blown a two-set lead in the French Open three times in the past, and each time he prevailed in the fifth. Leconte got the final service break in the eigth game and closed out the match on a service winner.

"Without the French fans, I could not have won this match," said Leconte, who only two years ago was roundly jeered in his straight-set loss to Mats Wilander in the final.FEATURED MATCHES Court Central

Steffi Graf (1), West Germany, vs. Conchita Martinez (9), Spain; Andre Agassi (3), Las Vegas, vs. Michael Chang (11), Placentia, Calif; Henri Leconte, France, vs. Jonas Svensson, Sweden; Jennifer Capriati, Saddlebrook, Fla., vs. Mary Joe Fernandez (7), Miami.Court 1

Monica Seles (2), Yugoslavia, vs. Manuela Maleeva (6), Switzerland; Katerina Maleeva (8), Bulgaria, vs. Jana Novotna (11), Czechoslovakia.