Top seed John Isner suffered a painful loss to Federico Delbonis in the quarter-finals of the Open de Nice Cote d'Azur.
The 6ft 10in American served for the match in the deciding set but was broken and went on to lose the tie-break in a 6-4 5-7 7-6 (8/6) defeat.
Second seed Ernests Gulbis and defending champion Albert Montanes both survived close battles and will meet in the semi-finals on Friday.
Gulbis won a deciding tie-break to beat Dmitry Tursunov 6-3 3-6 7-6 (7/5) while Montanes was a 6-7 (6/8) 6-4 6-4 winner over qualifier Leonardo Mayer.
Delbonis' opponent will be home favourite Gilles Simon, who defeated Carlos Berlocq 6-4 6-1.