SOFIA (Reuters) - A dominant Stan Wawrinka outclassed Serbian Viktor Troicki 6-1 7-6(3) to book his place in the semifinals of the Sofia Open on Friday and suggest that his recovery from a knee injury is well under way.

FILE PHOTO: Tennis - Australian Open - Hisense Arena, Melbourne, Australia, January 16, 2018. Stan Wawrinka of Switzerland celebrates winning against Ricardas Berankis of Lithuania. REUTERS/Toru Hanai

The 32-year-old Swiss, who had surgery in August and only returned to the court last month, offered fans at the Armeets Arena plenty of “oooh-aahh” moments with his trademark backhand winners.

“It was a great match, I played better than I expected,” said Wawrinka, aiming to clinch his first title since winning the Geneva Open in May.

“I’m improving every day, I’m moving better and I’m serving better. I think my level is getting better.”

Wawrinka’s semifinal opponent will be Bosnian qualifier Mirza Basic, who produced a solid display to beat Maximilian Marterer 6-4 4-6 6-3, claiming his second German scalp after eliminating fourth seed Philipp Kohlschreiber on Wednesday.

World number 93 Marius Copil fired down 13 aces to reach his first ATP semifinal with an impressive 6-4 6-4 victory over third seed Gilles Muller – his third consecutive straight sets win.

The 6ft 4in Romanian lost only three points on his serve before breaking for a 5-4 lead and wrapping up the opening set, winning the next game to love.

The second set was a tighter affair but Luxembourg’s Muller, one of the last of dying breed of players prepared to serve-and-volley, couldn’t find a solution to Copil’s aggression and accuracy.

Copil will face Slovakian qualifier Jozef Kovalik, who continued his fairytale week with a 7-6(2) 6-4 win over Cypriot Marcos Baghdatis, his fifth successive victory on Bulgarian soil.

World number 187 Kovalik needed all his firepower and mental strength to fend off the resilient Cypriot in a highly charged clash that lasted one hour and 55 minutes and reach his first ATP semifinal.

“This is the biggest win of my career,” a delighted Kovalik said in a courtside interview.