Matija Pecotic said he is going to "have to ask for another day off" from his full-time job in finance after a shock win at the Delray Beach Open.
Pecotic, who came through qualifying, was making his ATP Tour main draw debut against former world number eight Jack Sock and won 4-6 6-2 6-2 in Florida.
The 33-year-old Croatian hit 10 aces and 30 winners in a first-round match that lasted two hours and 10 minutes.
"I had to leave work early, my boss let me off," joked Pecotic.
And his boss watched on from his player box as the world number 784, who reached a career-high 206 in 2015, beat American Sock, who is 143 in the men's rankings.