When Daria Kasatkina cut her 2025 season short in October, the former world number eight described how she had "hit a wall".
"The schedule is too much. Mentally and emotionally I'm at breaking point and, sadly, I'm not alone," she wrote.
Ukraine's Elina Svitolina, a two-time Wimbledon semi-finalist, had already announced she was not in "the mental space" to continue, while reigning Grand Slam champions Iga Swiatek and Carlos Alcaraz believe the calendar is too long.
The topic continues to be debated as the world's leading tennis players reconvene in Australia for the start of the 2026 season.