World No. 1 Roger Federer of Switzerland has reached the semifinals of the Madrid Open tennis tournament in Spain, while No. 2 Rafael Nadal was upset before the home crowd.

Argentina's David Nalbandian took advantage of 29 unforced errors by Nadal on the indoor hard court surface en route to a lopsided 6-1, 6-2 victory. Nalbandian will next face third seed Novak Djokovic of Serbia. Djokovic won his quarterfinal over Croatian Mario Ancic, 7-6, 6-2.

Federer won his quarterfinal Friday over Feliciano Lopez of Spain, 7-6, 6-4. Lopez hit 28 winners in saving 10 service break chances, but he also committed 34 unforced errors against the top-seeded and defending champion Federer.

Federer's semifinal opponent will be the winner of Friday's late match between Nicolas Kiefer of Germany and Fernando Gonzalez of Chile.

Meanwhile, world No. 1 women's tennis player Justine Henin of Belgium had little difficulty reaching the semifinals of the Zurich Open in Switzerland, but two players failed to complete their quarterfinal matches Friday because of injuries.

Henin ran her record to 56-4 this year, booking her spot in the final four with a 6-4, 6-2 victory over Poland's Agnieszka Radwanska. She will next play Nicole Vaidisova of the Czech Republic, who beat Alona Bondarenko of Ukraine, 6-1, 6-4.

The women's world No. 2, Svetlana Kuznetsova of Russia and ninth seed Marion Bartoli of France were unable to finish their matches, allowing their opponents to make the final four.

Bartoli trailed countrywoman Tatiana Golovin 5-4 when she retired with a knee injury. Kuznetsova bowed out against Italian Francesca Schiavone because of a shoulder injury. Schiavone had won the first set, 6-3, and the two players were tied at three-all in the second set when Kuznetsova could not continue.

Kuznetsova and Bartoli were the third and fourth players this week to retire from a match because of injury. On Tuesday, sixth-seeded Serena Williams of the United States retired with a sore right thigh, and Russian Elena Dementieva pulled out with left thigh injury on Wednesday.

Some information for this report provided by Reuters, AP and AFP.