Top seed Stan Wawrinka and US Open champion Marin Cilic, the second seed, were both knocked out of the Geneva claycourt tournament on Thursday in the quarter-finals.
Wawrinka, who was looking to capture a first title on home ground, went down 6-7 (5/7), 6-4, 6-4 to Argentina’s Federico Delbonis.
Delbonis will next face Portuguese sixth seed Joao Sousa who saved four match points in the third set tie-break to prevail 6-4, 2-6, 7-6 (8/6) over third seed Pablo Andujar.
Santiago Giraldo of Colombia booked a spot in his second semi-final of the year when he recorded his first victory over Cilic in their fifth meeting.
Giraldo won 7-5, 6-3 and next faces Thomaz Bellucci of Brazil who saved eight of 13 break points in a 6-0, 1-6, 6-3 victory over Albert Ramos-Vinolas.