Frances Tiafoe might be in hot water after the American tennis star directed a profanity-laden outburst at an umpire following a controversial call at the ATP Shanghai Masters on Tuesday.

In a third-round match against unseeded Roman Safiullin, Tiafoe was penalized for a time violation while serving during a third-set tiebreaker. Tiafoe, seeded 13th for the tournament, lost his first serve, and Safiullin would win the point. The Russian would claim a 5-7, 7-5, 7-6 (5) win shortly thereafter.

After match point went Safiullin's way, Tiafoe greeted the Russian at the net for a typical post-match handshake before letting loose at umpire Jimmy Pinoargote (warning: video of the incident is not safe for work). "F--- you, man!," said Tiafoe. "F--- you! Seriously, man. F--- you! You f---ed me out of the f---ing match!"

Tiafoe continued his harangue, at one point stating that Pinoargote would be "on the blacklist" for the world No. 17's future matches as he made his way off the court. However, Tiafoe took to social media later on Tuesday to post an apology for his remarks.

The loss cost Tiafoe a chance to take on Novak Djokovic in the round of 16, which takes place Wednesday. At the time of publication, the ATP Tour had not issued a fine or punishment. The 2024 ATP Tour rulebook states that instances of verbal abuse at Masters 1000-level events can carry a fine of up to $60,000.

Here's what to know:

Tiafoe issues apology after outburst

After losing an extremely tight match in Shanghai, China, to Roman Safiullin, Frances Tiafoe exploded at umpire Jimmy Pinoargote, who had penalized the American over a time violation in one of the final points of the tiebreaker.

However, a few hours later, Tiafoe took to Instagram to offer an apology for the incident.

"I really apologize for the way I acted tonight," read an Instagram story posted to Tiafoe's account. "That is not who I am and not how I ever want to treat people. 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. I'll be better for yall [sic]."

Why did Tiafoe blow up at umpire Jimmy Pinoargote?

The issue between Tiafoe and Pinoargote came with the third-set tiebreaker level at 5-5. With the serve clock running low, Tiafoe tossed the ball up, but let it drop rather than going through with his serve.

Pinoargote immediately took to the microphone to announce a time violation, which meant Tiafoe lost his first serve. The implications on the match were simple: Tiafoe would no longer get the benefit of a fault, leaving him the choice of pushing the limits of his second serve and risking a double-fault (which would give Safiullin the point) or taking a conservative route to make sure the serve was in play.

"No, no, no, I tossed the ball," protested Tiafoe while approaching the bench. "I was at the line and I tossed the ball." Pinoargote replied "I'm not buying this, it's the second serve now."

Tiafoe continued to push his argument, saying "Dude, that's the rule! The ball goes up, how am I not ready to serve?" Pinoargote cut the exchange, announcing "second serve" on the microphone, leaving Tiafoe to head back to the line in clear frustration.

Safiullin would win the point after some clever play at the net, and would take the match by winning the next point in an upset victory.

What is the ATP Shanghai Masters?

The 2024 Shanghai Masters is one of nine ATP Tour events (collectively called the ATP Masters 1000) featuring the top-ranked players in tennis. In terms of prestige, the Masters 1000 tournaments are major titles, though they are one step below the four Grand Slams and the ATP Finals.

The Shanghai Masters, which began in 2009, is the only Masters 1000 tournament held outside of Europe or North America. The hard court tournament, won in 2023 by Poland's Hubert Herkacz, is held every October and features a 96-player draw to start. This year's tournament runs from October 4-15, with a total prize pool of $8,800,000.