GSTAAD, Switzerland -- Top-seed and world No. 2 Marcelo Rios of Chile advanced to the quarterfinals of the Swiss Open with a 6-4, 6-1 victory over Lucas Arnold of Argentina on Thursday.
Rios, who briefly replaced Pete Sampras as world No. 1 early this year, will next meet Spain's Francisco Clavet on Friday.
Clavet advanced with a 2-6, 6-4, 6-4 win over Gustavo Kuerten, ending the Brazilian's bid for his first title since winning the French Open last year.
Boris Becker, winner of six Grand Slam titles but now ranked 119th in the world, proved he still is a major force, defeating fourth-seeded Cedric Pioline 7-6 (7-2), 7-5.
"I played my best match of the year," Becker said. "I surprised myself. I don't think I can play much better than I did today."
The 30-year-old German is hoping his first appearance at the tournament might result in a 50th career singles title, and his first ever on clay.
"I still have a long way to go before perhaps winning my first title on clay," Becker said. "But if I serve as well as I did today, I have a chance."
The defeat offered nothing but continuing disappoinment for Pioline, who, for the seventh time in as many appearances, failed to advance past the second round of the tournament.
It also was the seventh time in seven matches that Pioline lost to Becker. Their last four matches all ended in straight sets.
In the quarterfinals, Becker will face defending champion and No. 5 seed Felix Mantilla of Spain. Mantilla beat France's Fabrice Santoro 6-4, 0-6, 6-2.
In a Spanish quarterfinal, third-seeded Alex Corretja will play No. 6 seed and 1996 champion Albert Costa. Corretja advanced with a 6-0, 7-5 win over Slava Dosedel of the Czech Republic and Costa beat compatriot Galo Blanco 7-6 (7-3), 6-3.
Eighth-seeded Nicolas Kiefer of Germany made the quarterfinals with a 6-3, 3-6, 6-1 win over Julian Alonso of Spain. The German will face Belgian Filip Dewulf, who posted a 3-6, 7-5, 6-3 victory Fernando Meligeni of Brazil.