Jannik Sinner's opponent jokingly accused him of "breaking" his racket by playing "too fast" during their Shanghai Masters semi-final.

Tomas Machac was up against it as he served to stay in the match while trailing the world No. 1 4-6 4-5.

He was forced to stop the game so he could change rackets before serving again after the frame appeared to disintegrate.

The Czech star had been broken at the exact same moment in the first set and was trying to give himself a lifeline in his first-ever Masters semi-final.

After losing the first point of the game, Machac suddenly sprinted to his bench and showed umpire Mohamed Lahyani why he needed to change his racket. "No problem," the chair official said before seeing the damage and exclaiming.

Before making the switch, the 30th seed wanted Sinner to see how bad it was. "Too fast. The rallies is too fast," he said, calling over to the Italian who was waiting at the baseline.

A confused Sinner rushed over to take a look before realising his opponent was joking.

"The racket is broken. You play too fast," Machac added before Sinner finally understood, laughing as they both returned to the court to resume play.

The Czech players hilarious reaction left the umpire and the commentators in stitches. "He’s serving to stay in the match in the semi-finals. That’s nice," Barry Cowan said on commentary.

Nick Lester replied: "Nice problem to have, shows he’s kind of embracing the moment. It’s not been an overwhelming occasion for him."

After the unusual interruption, Machac managed to hold on and drew level at 5-5. But it was the last game he won as Sinner broke to win 6-4 7-5.

With the win, he is guaranteed to finish the season as the year-end No. 1 for the first time in his career. "It’s amazing, no? It’s something what you dream of when you’re a kid, when you’re young, just to reach No. 1," Sinner said.

"Now having the year-end it’s also a new special feeling. But this happens during a tournament so I’m not even that looking forward to that.

"I know tomorrow it’s going to be an important day, finals is ahead. But it means to much to me obviously and this is something I could not accomplish without the people I have around and the family and friends and obviously also a big credit to my team."