FILDERSTADT.

Germany. Oct 9: Wimbledon champion Jana Novotna’s chances of l>ecomlng world number one for the first time took a blow when she retired in the second round of the Porsche Grand Prix with a back injury.

The world number three is still in contention, along with Martina Hingis and Lindsay Davenport, for the year-end top spot, but will have extra ground to make up after quitting two games into the final set against Serena Williams.

The 17-year-old American achieved her seventh quarterfinal in a tier two tournaments or better, but Williams' 2-6, 6-3. 2-0 win had looked unlikely when she was a set and a break of serve down.

In the third game of the second set it became apparent Novotna had lost some of her

ease of movement. Her ground strokes lost their variety and penetration, allowing Williams to develop a rhythm.

After breaking serve the teenager's confidence visibly escalated, and the match then became a painful tactical struggle for Novotna to find ways to hang on.

Three times the Czech took breaks from play, the first an injury time out when Williams reached set point at 5-3. 40-15 in the second set.

She left the arena, while Williams earned a round of ap-Silause from the crowd for pe.--orming a hundred skips on

"I knew I had to concentrate hard at that stage," said Williams. "I lost a match before when my opponent took Injury time out and 1 lost concentration."

This time Williams had to cope with a bathroom break

from Novotna within two points of the Injury break, and then another Novotr^ bathroom break after the first game of the final set.

However by then it was clear that Novotna's movement was not improving, and one game after that she apologised, shook hands and walked off for the last time.

Williams now plays Sandrine Testud. one of two French players to reach the last eight.

The other is Nathalie Tauziat who repeated her Wimbledon semifinal victory over Natasha Zvereva.

Within two hours there was another upset as Serena's sister, fifth-seeded Venus Williams, was blown away by an outstanding performance from Dominique van Roost.

The Belgian showed exquisite timing with flat ground strokes on a fast indoor court, hustling last weeks wumer of the Grand Slam Cup into a 6-1, 6-2 defeat.

"She played very well but 1 expected more from myself than this. I missed a lot of shots and I am very disappointed." said Venus.

The results worked well for Martina Hingis in her bid to win the tournament for a third time, she can now reach the final without meeting a seeded player.

However she has lost the chance of bonus computer points for beating seeds and the world number one ranking will now pass to US Open champion Lindsay Davenport if she can win her quarterfinal against Tauziat.