The governing body of men's tennis could consider a formal heat rule after a string of retirements at the Shanghai Masters this week blew the draw wide open, with top players wilting under soaring temperatures and punishing humidity.

World No. 2 Jannik Sinner's title defense ended in agony on Sunday when the Italian struggled to walk due to cramp in his right thigh before he retired in the deciding set of his third-round clash with Tallon Griekspoor.

Novak Djokovic vomited during his encounter with Yannick Hanfmann while Holger Rune was heard asking an official during a medical timeout in his meeting with Ugo Humbert if players had to "die on court" amid the heat and humidity.