The small furry objects that are the focus of every tennis player's energy are spinning the stars at the ATP finals into a fury and leaving them deflated.
"The balls are a big problem," said world No.2 Alexander Zverev.
Many of the top players say all the brands have deteriorated and most dislike playing with different makes of ball from one tournament to the next.
With your current subscription plan you can comment on stories. However, before writing your first comment, please create a display name in the Profile section of your subscriber account page.