HAMBURG, Germany -- Third-seeded Martina Hingis beat Cristina Torrens Valero 6-1, 6-0 Thursday to advance to the quarterfinals of the Betty Barclay Cup.

Hingis, who won the event in 1998 and 2000, was one of five seeded players to advance in the clay-court tournament.

Second-seeded Kim Clijsters reached the quarterfinals when Barbara Rittner pulled a right hamstring in the second set. Clijsters, ranked No. 3, was leading 6-3, 2-1 when the match was stopped.

Fourth-seeded Justine Henan beat Nicole Pratt 6-3, 6-4; Arantxa Sanchez-Vicario, seeded No. 8, beat 19-year-old wild card Martina Mueller of Germany 6-4, 2-6, 7-6 (7-4); and sixth-seeded Daniela Hantuchova beat Magui Serna 7-6 (7-5), 6-3.

Barbara Schett of Austria was the only unseeded player to reach the quarterfinals, beating German qualifier Anca Barna 6-1, 6-2.

Top-seeded Venus Williams advanced to the quarterfinals on Wednesday.