The first week of a Grand Slam tournament can be likened to the Tour de France before the first time-trial and the mountains. A lot can happen but it is rarely conclusive. "This has been the warm-up," said Martina Hingis yesterday. "The second week is the tournament for the stars."

Hingis, the number one seed, had just won 6-1, 6-2 against Israel's Anna Smashnova (a name that surely demanded she play tennis) to reach a quarter-final against Venus Williams tomorrow - one of the most eagerly awaited clashes of this French Open.

They last met just over two weeks ago in the Italian Open final, which Hingis won in three sets, her fifth win in seven meetings against the American.

Hingis refuses to be drawn into talk of rivalries. "You cannot really say there are rivalries right now," she said, a glint of steely arrogance behind her flashing smile. "Sure, Anna Kournikova and the Williams sisters are going to be very dangerous in the future, but right now they haven't won anything big. I've won four Grand Slams."

So she has. But the future may catch up with Hingis rather quicker than she would wish, unless she stays right on top of her game. Her serve remains vulnerable, although she believes it is improving with the rest of her game.

These are fascinating times in the women's game, although, for all the talk of the teenagers, what might be described as the old guard - Monica Seles, 24, and Arantxa Sanchez Vicario, 26 - are far from done.

Seles, a three-time champion here before the stabbing incident in 1993, also made it to the quarter-finals yesterday, beating her fellow American Chanda Rubin 61, 6-4. Rubin, 22, was once spoken of as a potential Grand Slam champion but serious wrist injuries have affected her career.

The day's most fascinating match involved Sanchez Vicario and the 16-year-old Serena Williams, playing only her second Grand Slam. Many believe that Serena will ultimately outstrip her sister, and the Spaniard, the champion here in 1989 and 1994, was expected to be given a tough ride.

Indeed, the younger Williams thundered to a 2-0 lead, the packed court gasping at the ferocity of her groundstrokes and the daring of her passes. But Sanchez Vicario quickly levelled and began to move the American from side to side like a pendulum.

Sanchez Vicario squeaked out of one tight jam as she served to save the first set, but neat volleying at the net saw Williams home. The Spaniard believed a shot had bounced twice during this rally and created merry hell with the umpire. Williams firmly pointed out that the Sanchez Vicario was talking through the holes in her racket.

Thereafter the tennis took over, save for what might have constituted a touch of gamesmanship midway through the second set when Sanchez Vicario visited the bathroom, and returned having changed her black dress for a white one.

There was no adverse affect on Williams, who broke her for a 4-2 lead which she extended to 5-2. But then the youngster's game began to unravel, probably out of tiredness.

Sanchez Vicario reeled off five successive games for the second set and thereafter took control to win 4-6, 7-5, 6-3. Serena, watched by Venus, who had earlier defeated Henrieta Nagyova of Slovakia 6-1, 6-3, will have learned a lot from this defeat.

Two other key women's fourth round matches remained unfinished as darkness descended last night.

Czech third-seed Jana Novotna was leading Anna Kournikova 6-7 (2/7), 6-3, 4-2 while defending champion Iva Majoli and seventhseed Conchita Martinez were deadlocked at one set all after two tie-breaks. Majoli won the first 7/1 and Martinez the second 7/3.

When the matches resume today, Novotna and Kournikova will be bidding to play Seles, while Majoli and Martinez are playing for a quarter-final showdown against second-seed Lindsay Davenport of the United States.

Marcelo Rios, the men's title favourite, reached the last eight with a 4-6, 6-4, 6-3, 6-3 win over Spain's Albert Costa. He next plays another Spaniard, Carlos Moya, whose compatriot Alex Corretja also went through after one of the longest matches in French Open history, a five-and-a-half-hour defeat of Argentina's Hernan Gumy.

Also into the last eight are Felix Mantilla, who beat Paraguay's Ramon Delgado 6-2, 6-2, 6-4 and Thomas Muster who beat Brazilian Fernando Meligeni 6-4, 6-7, (8/10), 3-6, 6-3.