Top seed Alexandr Dolgopolov crashed out in the second round of the Kremlin Cup in Moscow.
Dolgopolov had four match points against qualifier Edouard Roger-Vasselin of France before succumbing 6-3 5-7 7-6.
Roger-Vasselin, ranked a lowly 116 in the world, looked to be in trouble in the 12th game of the deciding set before upping his game and saving the first two of those match points.
Dolgopolov took a 6-4 lead in the tie-break but managed to lose the next four points to send Roger-Vasselin into the quarter-finals.
There was better news for second seed Andreas Seppi and fourth seed Thomaz Bellucci who moved into the last-eight with little trouble.
Seppi saw off Dutchman Igor Sijsling 7-5 6-2 while Bellucci crushed Flavio Cipolla 6-4 6-1.