One more match victory tomorrow, when he faces Karol Kucera of Slovakia, will guarantee the 22-year-old Chilean Rios the top spot on the ATP tour when the new rankings come out on Monday.

Five-time Wimbledon champion Pete Sampras will lose the ranking leadership if Rios reaches the final on the Weissenhof Club clay courts. Kucera reached the last four with a 6-4, 6-4 victory against Bohdan Ulihrach, improving his record against the 53rd-ranked Czech to 3-0.