Australia's Michael Matthews has maintained his lead of the Paris-Nice race but Alexey Lutsenko cut the Orica rider's advantage to six seconds after winning the mountainous fifth stage on Friday.
Lutsenko surged away 15km from the end of the hilly route and finished 21 seconds clear of Alexander Kristoff who won the bunch sprint for second place ahead of Matthews in third.
"The priority was the yellow jersey more than the stage win," Matthews said.
"I'm not going to say I can win Paris-Nice, but I'm going to give it everything I have."
The 198km route to Salon-de-Provence featured the famed Mont Ventoux, one of the most feared climbs on the Tour de France.
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Kristoff tried to stay on Lutsenko's wheel, but dropped off as Lutsenko accelerated on the fifth and final climb up Col de Seze and rode away to victory.
Saturday's penultimate sixth stage stays in the mountains, featuring seven climbs.
