Spraying errors throughout against eighth-seeded Amanda Coetzer, Williams lost 6-3, 6-4 Friday in the quarterfinals of the clay-court Betty Barclay Cup.

``It's bitter,'' said Williams, the defending champion and second seed at the $535,000 tournament, her first event since November because of tendinitis in both wrists.

Williams won in three sets against Irina Spirlea on Thursday. But the American's lack of match practice showed dramatically against Coetzer, a player Williams had beaten in all four previous encounters, including last year on the way to the Hamburg title.

A double-fault by Williams gave Coetzer the first set and Williams was hardly able to win a point again until late in the second set.

``She played well and I didn't play my best tennis,'' Williams said, ``that's the story of the match.''

Coetzer's semifinal opponent will be three-time Hamburg champion Arantxa Sanchez-Vicario. The fourth-seeded Spaniard ousted Andrea Glass of Germany 6-3, 6-3.

On the other side of the draw, Martina Hingis rallied from a set down to beat former doubles partner Anna Kournikova, setting up a semifinal showdown against streaking Anke Huber. Hingis beat the sixth-seeded Russian 3-6, 6-2, 6-4.

``I didn't play very well and Anna fought very well,'' the top-seeded Hingis said. ``It's encouraging to be able to win a match like this.''

Huber extended her winning streak on clay this year to 11 matches, fighting back to upset third-seeded Conchita Martinez 6-7 (6), 7-6 (4), 6-2.

Kournikova dominated the first set against Hingis with a big forehand and a nearly error-free performance. But she was unable to maintain the high level and allowed the Swiss star to come back.

Hingis led 5-1 in the third but Kournikova saved three match points and won the next three games before tumbling to her eighth loss in nine matches against Hingis, who is seeking her third title of the year.

If she wins the tournament, Hingis will recapture the No. 1 ranking she lost to Lindsay Davenport last month.

Huber, a German trying to get back into the Top 10 after a long slump, wasted three set points in the opening set, but fought back in an even match that could have gone either way.