World No. 2 Jannik Sinner had to be helped off the court in the third set at the Rolex Shanghai Masters, with severe cramping in his right thigh forcing him to retire from his third-round match against Tallon Griekspoor of the Netherlands on Sunday.

Griekspoor, the No. 27 seed, was leading 6-7 (3), 7-5, 3-2 when Sinner, limping around the court, ended the match. Griekspoor advanced to the fourth round.

That match capped a humid day on the court that left players feeling discomfort. Just ask Novak Djokovic, the No. 4 seed, who needed three sets to get past German qualifier Yannick Hanfmann 4-6, 7-5, 6-3.

"It's the same for every player out on the court, but it's brutal," Djokovic said of the weather conditions in Shanghai, where the daytime high was 92 degrees with 89 percent humidity.

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