For a noncontact sport, tennis has long had a high attrition rate. The grind of the international travel and the extended rallies often adds up to trouble.

But there has never been a season quite like this in modern men’s tennis: one where so many leading players have failed to reach the finish line.

“To me it doesn’t set off a red light; it sets off a yellow light,” said Paul Annacone, a former pro who later coached Pete Sampras, Tim Henman and Roger Federer. “Let’s see if it continues. I think it’s been one of those years, but if it goes into 2018, then I would start to go: What is happening? What are we doing? Is it the physicality? The heaviness of the balls? The length of the season?”

For now, no major course corrections are in the offing, but there is no doubt that it is not a good look when so much star power is missing from the year’s final Masters 1000 event, the Paris Masters, which is set to begin on Monday and is supposed to be a mandatory tournament for the men’s elite.