DUESSELDORF, Germany (AP) -- Qualifier Guido Pella of Argentina advanced to his first semifinal match on the ATP Tour by beating seventh-seeded Viktor Troicki 7-6 (5), 7-5 in the Power Horse Cup on Thursday.
A day earlier, Pella upset top-seeded Janko Tipsarevic.
The 101th-ranked Pella plays third-seeded Juan Monaco in an all-Argentine semifinal. Monaco defeated Tobias Kamke 6-3, 6-4. Monaco is the highest-seeded player left in the clay-court tournament, a warmup for the French Open.
Sixth-seeded Jarkko Nieminen of Finland will meet Igor Sijsling of the Netherlands in the other semifinal on Friday. Nieminen advanced when second-seeded Tommy Haas of Germany withdrew with a cold.
Sijsling reached his first semifinal with a 6-3, 6-1 victory over Jan Hajek.