Mikhail Youzhny stunned Milos Raonic, knocking the world number six out of the second round of the St Petersburg Open.

Raonic was eliminated in the second round of the US Open to Ryan Harrison, and was humbled at the same stage of this competition at the hands of the Russian veteran, going down 2-6 7-6 (8-6) 6-4.

Youzhny has won more matches in St Petersburg than any player on the ATP Tour, and had to work hard for his 33rd victory at the tournament.

The Canadian, finalist in Wimbledon this year, dominated the opening set taking it in 33 minutes and conceding just two points on his booming serve.

Victory was in Raonic's grasp at 5-1 up in a second-set tie-break, but Youzhny produced an incredible surge to take the next five points, before taking the contest to a deciding set at the second attempt.

Youzhny's battling instincts were on full display in the decider, saving 10 break points across two of his service games, but it was a second match point that had the home crowd on their feet.

Rising star Alexander Zverev awaits the veteran in the quarter-finals after he beat Russia's Daniil Medvedev 6-3 7-5.

Third seed Tomas Berdych scrapped past Andrey Kuznetsov in three sets and faces Paolo Lorenzi next.

Joao Sousa and Viktor Troicki were also winners on Thursday.