Jannik Sinner declined his spot at the ATP Next Gen Finals which allows rising star Holger Rune to play at the event.
Sinner has played and won the ATP Next Gen Finals before but the Italian won't be making an appearance in 2021. Although eligible to play Sinner opted against playing as he is still technically in the fight for a place in the ATP Finals in Turin. The Next Gen ones in Milan won't feature Sinner but they will feature Holger Rune instead.
The Danish player has been a rising star this season climbing very high on the rankings compared to where he started his year. He will have a chance to flash his talents in Milan amongst some of the best young players in the world.
Sinner's season did not end in Paris with the loss to Alcaraz as the Italian will travel to Stockholm for the final event of the year. There is a slight chance he could book a spot in Turin with a trophy there but it's highly unlikely.