see more

GUANGZHOU, CHINA - MARCH 20: Lukas Lacko of Slovakia serves during the match against Ze Zhang of China during the 2016 'GDD CUP' International ATP Challenger Guangzhou Tour Day 6 at Guangzhou Development District International Tennis School on March 20, 2016 in Guangzhou, China. (Photo by Zhong Zhi/Getty Images)

GUANGZHOU, CHINA - MARCH 20: Lukas Lacko of Slovakia serves during the match against Ze Zhang of China during the 2016 'GDD CUP' International ATP Challenger Guangzhou Tour Day 6 at Guangzhou Development District International Tennis School on March 20, 2016 in Guangzhou, China. (Photo by Zhong Zhi/Getty Images)