ROME (AP) -- Martina Hingis taught Serena Williams a simple truth of clay-court tennis Friday: Patience is a virtue.

The Italian Open's defending champion and top seed dominated the rushing Williams from the start and routed the American, 6-2, 6-2, to set up a semifinal clash with Serena's sister, Venus.

Hingis reeled off 16 of her quarterfinal match's first 17 points and gained a measure of revenge for her loss in the players' prior meeting, on a hard court at the Lipton Championships in March.

``I just didn't miss. I was very focused, and didn't let her back in the game,'' Hingis said. ``And I just didn't give her the chance to kill me. I guess I made her kill herself.''

Venus Williams, seeded third, advanced with a 7-6 (7-1), 6-2 win at night against No. 11 Dominique Van Roost. The Belgian suffered a right groin strain early in the second set and could not keep up with Williams thereafter.

Hingis and Venus Williams have been the tour's top two players this season, each with three titles.

``Another Williams is on the way,'' Hingis said. ``Beating the whole family all the time is not easy. They're very powerful, the best out there.'' She has a 6-2 career record against Venus, and has won both of their encounters on clay, including last year's Rome final.

Mary Pierce, the 1997 Italian Open champion, and fellow Frenchwoman Amelie Mauresmo, a surprise finalist at the Australian Open, also won Friday and will meet in Saturday's other semifinal.

The 10th-seeded Mauresmo ended Sylvia Plischke's string of upsets with a 6-2, 6-3 win over unseeded Austrian. Plischke had beaten French Open titlist Arantxa Sanchez-Vicario and 12th seed Amanda Coetzer.

Pierce, seeded fourth, beat another French player, No. 8 Sandrine Testud, 6-4, 7-5.

Williams family pride will be on the line against Hingis.

``We have a saying: If I can't do it for myself, I'll do it for (my sister),'' Venus said.

Serena has been on a roll in 1999, winning her first two career titles, and had dropped just eight games in two matches here. But the sixth seed got into trouble Friday by trying to force the action, compiling more than two dozen unforced errors in the 62-minute encounter.

``I didn't make any shots out there. You could probably count the number of shots I made -- two or three,'' Williams said. ``She didn't really win. I gave it to her. I made so many errors, it was really, absolutely absurd.''