Martin Klizan of Slovakia returns the ball to Stan Wawrinka of Switzerland during their St. Petersburg Open 2018 semi final tennis match on September 22, 2018 in Saint Petersburg, Russia. (Photo by Mike Kireev/NurPhoto via Getty Images)
Martin Klizan of Slovakia returns the ball to Stan Wawrinka of Switzerland during their St. Petersburg Open 2018 semi final tennis match on September 22, 2018 in Saint Petersburg, Russia. (Photo by Mike Kireev/NurPhoto via Getty Images)