Second-seeded Gilles Simon of France and third-seeded Sam Querrey of the US were eliminated in the quarter-finals of the Open de Nice on Thursday.
Spaniards Alberto Montanes and Pablo Andujar and Frenchmen Gael Monfils and Edouard Roger-Vasselin reached the last four.
Wild-card entry Roger-Vasselin beat Querrey 3-6, 7-6 (7/2), 6-1. The Frenchman broke Querrey twice in the final set to lead 5-1, before converting his first match point with a forehand winner.
Roger-Vasselin is to next play clay-court specialist Montanes. The Spaniard beat Paul-Henri Mathieu of France 6-4, 6-1.
A semi-finalist at the Madrid Open earlier this month, Andujar stunned Simon 6-4, 7-5. The Spaniard hit a drop shot to break Simon at 4-4 in the opening set, before rallying from a 4-1 deficit in the second.
Andujar is to meet Monfils, who ousted Robin Haase of the Netherlands 6-2, 6-3.
A former top 10 player, Monfils won the last five games. The Frenchman has been bothered by a right-knee injury last year, dropping to 109th in the rankings.
POWER HORSE CUP
AP, DUSSELDORF, Germany
Qualifier Guido Pella of Argentina advanced to his first semi-final match on the ATP Tour by beating seventh-seeded Viktor Troicki 7-6 (7/5), 7-5 in the Power Horse Cup on Thursday.
The 101th-ranked Pella is to meet third-seeded Juan Monaco in an all-Argentine semi-final. 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 is to meet Igor Sijsling of the Netherlands in the other semi-final. Nieminen advanced when second-seeded Tommy Haas of Germany withdrew with a cold.
Sijsling reached his first semi-final with a 6-3, 6-1 victory over Jan Hajek of the Czech Republic.