Sofia Open: Stan Wawrinka reaches first semi-final since knee surgery with win over Viktor Troicki

Stan Wawrinka celebrates winning a point against Viktor Troicki. Image courtesy: Twitter/@sofiaopentennis[/caption]“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 semi-final 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 6'4 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.