His victory over Costa gave the third-seeded Rios, the highest seed left in the event, a first taste of things to come as he pursues his first Grand Slam title.

The Chilean now meets Carlos Moya before a potential semifinal clash with another Spaniard, Felix Mantilla, in the last four.

Costa played a fine first set against Rios, but then the Chilean rediscovered the devastating game which made him a world number one for three weeks last month.

Rios, who received massage to his left leg during the match, contested a few calls, looked as indifferent as ever to the obvious hostility from the crowd and angrily turned down questions from a TV interviewer after the match.

The ultimate set was especially dramatic as Costa, in turn, lost his temper on a disputed call in the sixth game, grabbed umpire Bruno Rebeuh by the sleeve in anger and collapsed fromthen on, losing the match in two hours and 38 minutes. Dewulf wolves down Clavet

Belgian Filip Dewulf, who saves his best tennis for his visits to Roland Garros, raced into the quarter-finals today when he outplayed Spaniard Francisco Clavet 7-5, 6-3, 6-1.

The 26-year-old Belgian, a semi-finalist last year, now plays either Spain's 14th seed Alex Corretja, who reached the last eight beating Australian Jason Stoltenberg.

Kournikova out

Czech veteran Jana Novotna sent teenager Anna Kournikova of Russia spinning out here today. A stoppage for poor light last night had given the 16-year-old Russian a brief respite as she had been trailing 2-4 in the decisive set.

But Kournikova could not make up for lost time and bowed out 6-7, 6-3, 6-3 in just over two hours.

The outcome had been almost inevitable after Kournikova's game deserted her shortly before dusk yesterday. The 13th seed went 4-0 down in the third set.

How The Seeds Fared

Men's singles: Hicham Arazi (Morocco) bt 16-AlbertoBerasategui (Spain) 6-2, 6-4, 3-6, 6-3; 14-Alex Corretja (Spain) bt Jason Stoltenberg (Aus) 6-4, 6-4, 6-3.

Women's singles (4th round): 3-Jana Novotna (Czech Rep) v Anna Kournikova (Rus) 6-7 (2-7) 6-3 4-2. Bad light stopped play; 4-Arantxa Sanchez-Vicario (Spa) bt Serena Williams (US) 4-6 7-5 6-3; 6-Monica Seles (US) bt Chanda Rubin (US) 6-1 6-4; 7-Conchita Martinez (Spa) v 10-Iva Majoli (Cro) 6-7 (1-7) 7-6 (7-3). Bad light stopped play;

Fourth Round Results

Men's singles: Filip Dewulf (Bel) bt Francisco Clavet (Spa) 7-5, 6-3, 6-1.

Women's singles: Patty Schnyder (Swi) bt Magui Serna (Spa) 6-1, 6-3.