Tennis world No.17 Frances Tiafoe apologises for yelling ‘horrible’ expletives at chair umpire

American tennis star Frances Tiafoe has apologised for an expletive-laden outburst at a chair umpire after losing his second-round match at the Shanghai Masters.

The world No.17 lost a close tiebreaker in the match-deciding third set against Russian 27-year-old Roman Safiullin, 7-5 5-7 6-7 (5-7) but blamed it on the official.

WATCH THE VIDEO ABOVE: Frances Tiafoe unleashes expletive-laden outburst.

With the match in the balance at 5-5 in the third set tiebreak, Tiafoe lost his first serve because of a time violation.

Incredulous, Tiafoe protested the call, arguing that he should have avoided the penalty because he had already thrown the ball in the air twice as practice.

“No, no, no — I tossed the ball up!?” Tiafoe could be heard saying, and repeating, after being called for the violation.

“I was at the (base) line and I tossed the ball.”

Not having a bar of it, the umpire firmly responded: “I’m not buying this, it’s the second serve now.”

“I tossed the ball, I’m ready to serve! Dude, that’s the rule; the ball goes up, how am I not ready to serve?” Tiafoe argued.

“Second serve,” he was met with by the umpire.

With his tail between his legs, the American dawdled back to the baseline and took his second serve, eventually losing the point after a long rally, leaving him match point down.

He went on to lose the next point and cough up the match.

Tiafoe held his frustration in while shaking Safiullin’s hand, but let loose immediately after.

Walking towards the umpire after shaking hands with his opponent, the 26-year-old let loose.

“F*** you, man. F*** you. Seriously man, f*** you. You f***** me in the f****** match,” the yelled, to the gasps of the crowd.

“Three f****** hours and you’re going to do that. Why? You f***** the match up. Great f****** job. F*** you.”

Tiafoe is likely to receive a big fine from the ATP for his outburst.

“ATP social media totally ignored Safiullin’s win over Tiafoe and… this is why,” tennis reporter Jose Morgado said.

“Horrible behavior from Frances, who should expect a big fine.”

With the dust settled the next morning (local time), Tiafoe made a self-reflective post, apologising for his outburst.

“I really apologise for the way I acted tonight,” he wrote.

“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 apologise to the umpire, the tournament, and the fans.

“I’ll be better for y’all.”