World number three Carlos Alcaraz has criticised the congested tennis calendar, saying "they are going to kill us in some way".
The 21-year-old spoke about the issue after beating American Ben Shelton in the Laver Cup, which is the Spaniard's 14th tournament of the year.
Alcaraz has claimed two Grand Slams this year, winning the French Open and Wimbledon, while he also earned a silver medal at the Olympics in Paris this summer.
He suffered a shock second-round loss to Dutchman Botic van de Zandschulp at the US Open in August, losing in straight sets.