Top seed Alexander Dolgopolov crashed out of the Kremlin Cup on Thursday, losing to French qualifier Edouard Roger-Vasselin in a dramatic tiebreak.
Dolgopolov had four match points, two of them in the tiebreak, before world No. 106 Roger-Vasselin surged back to win with his first match point in a 6-3, 5-7, 7-6(6) victory over 20th-ranked Dolgopolov.
"Maybe luck," Roger-Vasselin said when asked what had made the difference.
"He missed one or two easy shots on the match point but otherwise it was very close."
Roger-Vasselin will now play either big-serving Croatian world No. 79 Ivo Karlovic or Russia's 92nd-ranked Alexander Bogomolov Jr.
"They are both very good players. I've never played against Karlovic, so maybe it would be fun to play against him."
Dolgopolov said he had not used his chances to win the match before the tiebreak.
"I didn't use my chances to well in the third set," he said. "I had chances for a break."
Roger-Vasselin beat Bogomolov in their only previous meeting, on grass in June.