Hingis battles through, but Serena pulls out

World number one and defending champion, Martina Hingis battled her way into the quarter-finals of the WTA Tour Chase Championships with a 7-6 (7/5) 7-6 (7/5) victory over France's Sandrine Testud in New York.

World number one and defending champion, Martina Hingis battled her way into the quarter-finals of the WTA Tour Chase Championships with a 7-6 (7/5) 7-6 (7/5) victory over France's Sandrine Testud in New York.

Hingis advanced to a meeting with another Frenchwoman, fifth-seeded Mary Pierce, who defeated Russian Anna Kournikova on Monday.

It will be the third successive year that Hingis has met Pierce in the quarter-finals. Pierce beat Hingis in 1997 en route to the final but Hingis prevailed last year en route to the title.

Dominique Van Roost of Belgium was scheduled to face fourth seed Serena Williams of the United States, but Williams - the reigning US Open champion - withdrew after suffering a back injury in her morning practice session.

Serena Williams was replaced in the draw by Elena Likhovtseva of Russia, who gave Van Roost had a much easier game than expected in her first-round match, losing 6-2 6-3, in just over an hour.

Van Roost advanced to a meeting with sixth seed Nathalie Tauziat of France, who posted a comfortable 6-3 7-6 (8/6) victory over South African Amanda Coetzer.

Williams, from the United States, was treated by the tournament physician, Dr Ken Montgomery, who described the injury as a "vertebral dysfunction."

Williams said she felt excruciating pain in the upper left side of her back.

"I didn't feel anything pop or pull, but all of a sudden I couldn't move, run, walk, and even the simplest task of breathing became nearly impossible," she said.

Williams was seeded fourth in the 16-player, season-ending tournament that features a $2 million purse.

She had the best won-lost record on the WTA Tour this year, 41-7, and had lost just twice since late May while playing a reduced schedule.

She won her first Grand Slam tournament title two months ago in New York, defeating Martina Hingis in the final of the US Open shortly before her 18th birthday. Last month, she won the Grand Slam Cup, defeating older sister Venus in the title match.

The 18-year-old star won five singles titles this year - Paris Indoors, Indian Wells, Los Angeles, the US Open and the Grand Slam Cup - and was a finalist at Key Biscayne, Florida. Venus withdrew from the Chase Championships last year because of an injury.

The Williams sisters also had qualified for the Championships in doubles after winning both the French and US Opens this year. With Serena injured, they withdrew from the doubles and their place was taken by Conchita Martinez of Spain and Argentina's Patricia Tarabini.

Earlier on Tuesday, Nathalie Tauziat defeated South African Amanda Coetzer 6-3, 7-6 (8-6) in a first-round match. Tauziat became the second French player to advance to the quarter-finals.

Tauziat, the No 6 seed, dominated the 5-foot-2 Coetzer in the opening set, which took only 29 minutes.

"I never had a chance," Coetzer said. "I just think she played a flawless set."

In the quarter-finals, Schett will face the winner of the Venus Williams-Martinez match.

The opening round will be completed today, beginning with a day match between No 8 Julie Halard-Decugis of France and Germany's Anke Huber. At night, No 2 Lindsay Davenport, the Wimbledon champion, plays Amelie Mauresmo of France and third-seeded Venus Williams takes on Spain's Conchita Martinez.

Singles First Round (seeds in brackets)

Nathalie Tauziat (6), France, beat Amanda Coetzer, South Africa, 6-3, 7-6 (8-6).Dominique Van Roost, Belgium, beat Elena Likhovtseva, Russia, 6-2, 6-3.Martina Hingis (1), Switzerland, beat Sandrine Testud, France, 7-6 (7-5), 7-6 (7-5).Mary Pierce, France beat Anna Kournikova, Russia 6-7 (3-7), 7-6 (7-5), 6-0. Barbara Schett, Austria beat Arantxa Sanchez-Vicario 6-1, 6-4.

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Doubles First Round

Arantxa Sanchez-Vicario, Spain, and Larisa Neiland, Latvia, beat Irina Spirlea, Romania, and Caroline Vis, the Netherlands, 3-6, 6-2, 6-3.Lindsay Davenport and Corina Morariu (2), United States, beat Conchita Martinez, Spain, and Patricia Tarabini, Argentina, 6-0, 7-5.