Alejandro Davidovich Fokina defeated world No 8 Andrey Rublev 7-5, 6-4 to reach the Barcelona Open quarterfinals on Thursday.
The Spaniard, ranked 30th, had never beaten the Russian before but triumphed at the sixth time of asking in straight sets.
Monte Carlo Masters semifinalist Davidovich Fokina broke three times in a topsy-turvy first set, with Rublev twice reacting before the Malaga native held to love in the 12th game.
Rublev went a break down in the first game of the second set, but despite securing one of his own for 2-2, he was once again broken as Davidovich Fokina took a 5-4 lead and then served out for the match, again to love.
Earlier, Spain's Jaume Munar came up short against Karen Khachanov, who also won 7-5, 6-4, and will face Davidovich Fokina in the next round.
The Russian, who trains in Barcelona, only converted four of 15 break points but eventually put the battling Munar to bed.