A part-time tennis player and full-time real estate professional beat the former No. 8 men’s player in the world at the Delray Beach Open in Florida on Tuesday.
Matija Pecotic from Croatia defeated Jack Sock, who reached No. 8 in the world in November 2017, in three sets to move on to the round of 16.
Pecotic, 33, is a director at a real estate investment firm and said he had to take some time off from work in order to compete.
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"I had to leave work early today," Pecotic said, according to ESPN. "I had to send an email to the whole team. [My boss] let me off. I'm going to have to ask for another day off tomorrow."
The 33-year-old reached a ranking of 206th in 2015 but suffered through complications following a surgery.
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He defeated Sock 4-6, 6-2, 6-2 on Tuesday, nailing 10 aces during the match.
Sock has 180 wins in his career with career earnings of nearly $12 million.
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"You've got to be realistic," Pecotic said. "This is a former top-10 guy with an incredible amount of tennis experience and a huge serve. He came out serving 134 mph on the first serve. It would be arrogant to think I'm going to come out and expect to win.
"But I figured if I could sink my teeth into the match and work on the two or three patterns I prepared before, that I'm going to have a chance."
Pecotic says he tries to train every morning with his real estate boss and loves the game of tennis.
His next opponent is American Marcos Giron, who is ranked No. 55 in the world.