Local favourite Mikhail Youzhny claimed a big scalp at the St. Petersburg Open on Thursday, knocking out second seed Milos Raonic.
The result sees the unseeded Russian move on to the quarter-finals, where he will take on fifth-seeded German Alexander Zverev, who was a 6-3, 7-5 winner over Daniil Medvedev.
Raonic appeared to be on course for a relatively straightforward victory after taking the first set 6-2 courtesy of successive breaks in game five and seven.
Raonic then broke in the ninth game of the second set and had an opportunity to serve for the match at 5-4, but Youzhny's fightback was about to begin.
He regained the lost break immediately, and then did the same again after Raonic broke again in game 11. That left a tie-break to decide the matters, which went to Youzhny by the narrowest of margins.
It all came down to a deciding third set and Youzhny would claim what turned out to be the decisive break in the ninth game to take a 5-4 lead.
Raonic fought bravely to prevent his opponent from serving out the match, earning no less than five break points during the 10th game, but Youzhny saved them all before finally succeeding on his second match point to claim a 2-6, 7-6 (8-6), 6-4 victory.
Also advancing on Thursday was seventh seed Viktor Troicki, who set up a quarter-final clash with top seed Stan Wawrinka after defeating Dusan Lajovic 6-4, 6-4.
Others to advance on the day included third seed Tomas Berdych, Joao Sousa and Paolo Lorenzi.