Marcos Baghdatis handed Frenchman Richard Gasquet only his second loss of the season as the Cypriot scored a 6-4, 6-4 win to reach the quarter-finals of the Rotterdam World Tennis on Thursday.
Gasquet lined up in Rotterdam as the fourth seed, having already won two tour titles this season and boasting an unbeaten record apart from a defeat to compatriot Jo-Wilfried Tsonga at the Australian Open.
But the world number 10 never got going against Cypriot Baghdatis, who had also beaten him at the London Olympics last year.
"Richard was probably tired, he's played a lot of tennis this season," said Baghdatis.
"He was not at his best and tired from last week," he added, in reference to Gasquet's run to victory in Montpellier.
"I'm happy with how I played. I was aggressive at the right time and served well. It's good to win a match like this."
Baghdatis won in 76 minutes with nine aces and two breaks of serve and will now face Bulgarian Grigor Dimitrov on Friday.
Meanwhile, Finn Jarkko Nieminen beat German qualifier Matthias Bachinger 6-3, 5-7, 6-3.
Bachinger had caused a surprise on Wednesday when he eliminated Italian sixth seed Andreas Seppi.