Every year players are pushed to their limits in a sport that chases the sun. But the number of retirements, withdrawals and injuries this season has been shockingJannik Sinner had tried everything but after baking for two and a half hours inside the suffocating sauna of Shanghai’s stadium court, he was finished. Even around midnight, the humidity was still so oppressive that Sinner had spent the final 20 minutes of his third-round match against Tallon Griekspoor cramping, panting and in considerable pain. Eventually, he could not even walk properly. Midway through the final set, the 24-year-old hobbled slowly to his chair using his racket as a crutch and terminated the match.Those scenes were representative of the Shanghai Masters so far as, throughout the past week, so many players have wilted in brutal conditions. Terence Atmane and Hamad Medjedovic both retired after struggling with the heat. Francisco Comesaña appeared close to collapsing and he had to be helped mid-match by hi...