Jan-Lennard Struff shocked Jo-Wilfried Tsonga to reach the semi-finals of the St Petersburg Open on Friday.

Second seed Tsonga suffered a 3-6 6-3 6-2 defeat to Struff, who denied the Frenchman a 30th match win of the year.

Tsonga was a set and a break up but eighth seed Struff produced a marvellous comeback to set up a semi-final with Damir Dzumhur, who ended qualifier Liam Broady's run with a three-set triumph.

Top seed Roberto Bautista Agut had no such problems against Viktor Troicki, cruising to a 6-1 6-2 victory to reach the last four of the event for the third successive year.

"The score looks easy, but the match wasn't," said Bautista Agut. "Viktor is always tough to beat, a very good fighter and serves well."

He will now face third seed Fabio Fognini for a place in the tournament showpiece, the Italian having hammered Ricardas Berankis 6-3 6-0 in under an hour.