Frances Tiafoe directed an expletive-filled tirade at a chair umpire after losing his third-round match Tuesday at the ATP Shanghai Masters event.
Tiafoe lost to unseeded Roman Safiullin 5-7, 7-5, 7-6 (5), minutes after chair umpire Jimmy Pinoargote called a time violation on the 13th-seeded American's service.
After congratulating Safiullin at the net, Tiafoe pointed at Pinoargote and shouted, "F--- you, man! F--- you! Seriously, man. F--- you! You f---ed me out of the f---ing match!"
Tiafoe added he had been battling on court for three hours for his livelihood, peppering his words with more expletives.
Tiafoe initially protested with the final-set tiebreak tied at 5-5, when Pinoargote called him for the time violation, which cost Tiafoe his serve. Tiafoe had tossed the ball in the air, though it was unclear if it was an attempt to serve.
"No, no, I tossed the ball up. ... I was ready to serve," Tiafoe said to Pinoargote. "Dude, that's the rule."
"I'm not buying it, it's the second serve," responded Pinoargote, who then ended the exchange by announcing "second serve" into the microphone.
Tiafoe went on to lose the point and eventually the match. Before leaving the court, Tiafoe added: "Never again."
Tiafoe posted an apology on Instagram later Tuesday.
"That is not who I am and not how I ever want to treat people," he said. "I let my frustration in the heat of the moment get the best of me and I'm extremely disappointed with how I handled the situation. That's not acceptable behavior and I want to apologize to the umpire, the tournament, and the fans."
Tiafoe could face fines for verbal abuse of an official and for using obscenities. The tournament can take away some of his prize money, and the case could also be sent to the ATP member fines committee for further investigation.
The ATP rulebook calls for fines of $60,000 at Masters 1000 tournaments. A tour spokesman said no decision has yet been made on the matter.
Safiullin next will face world No. 4 Novak Djokovic, who beat Flavio Cobolli in straight sets to move closer to his 100th career ATP title.
Tiafoe, 26, had a stellar run of form in the summer. He reached the final of the Cincinnati Open, where he lost to Jannik Sinner, then the US Open semifinals, where he lost in five sets to fellow American Taylor Fritz.
The Associated Press and Reuters contributed to this report.