German Tennis Federation (DTB) president Dietloff von Arnim has questioned the participation of some top stars at an exhibition tournament in Saudi Arabia this week amid a debate on a congested tour calendar.

“We are hearing again and again that the top players are complaining about the big strain in the tournament calendar. If someone complains about the big strain and then plays a show event then that is a bit strange,” von Arnim told dpa.

French Open and Wimbledon champion Carlos Alcaraz and Alexander Zverev are among players who have criticised the workload. Alcaraz expressed fear that having even more events in the future “will kill us.”

Alcaraz is among six players to feature at the October 16-19 Six Kings Slam in Riyadh. The others are world No 1 Jannik Sinner, men’s record grand slam winner Novak Djokovic, Holger Rune, Daniil Medvedev and retirement-bound Rafael Nadal.

Each players reportedly gets an appearance fee of US$1.5 million. The winner’s cheque is said to be US$6 million, which would be almost double what Sinner got for his US Open title last month.