Reacting to Dominic Thiem's retirement, 20-time Grand Slam winner Roger Federer said that Thiem always found a way to beat him with his thunderous backhands no matter what the surface was. "But more importantly, you did it with grace and sportsmanship," Federer said on Instagram. Thiem lost his last match 6-7 (6), 2-6 against Italy's Luciano Darderi in Vienna Open.