Karen Khachanov defeated Czech teenager Jakub Mensik to win his sixth career title at the Qatar ExxonMobil Open in Doha.
Nagal is the first Indian to feature in singles top 100 since Prajnesh Gunneswaran made the cut in 2019.
Carlos Alcaraz, Jannik Sinner, Daniil Medvedev and Holger Rune will also play at the 'Six Kings Slam', which will form part of the Saudi cultural and entertainment festival Riyadh Season.
A sell-out crowd in Turin's Pala Alpitour had hoped to cheer the 22-year-old Sinner to the biggest title of his career but Djokovic was simply in a different league.
The 20-year-old Alcaraz, who also has won six titles this season, missed out on becoming the youngest finalist in the season-ending tournament since Pete Sampras in 1991.
Alcaraz will face Green Group runner-up Novak Djokovic in a mouth-watering semifinal.
Home favourite Sinner also clinched top spot in the group with a 3-0 record.
The 20-year-old Alcaraz will need to beat Medvedev in his final group game on Friday.
The earlier Green Group clash was a non-event as Stefanos Tsitsipas retired injured against Holger Rune.
Rublev, ranked fifth in the world, began to despair after losing the first set and failed to put up much of a fight in the second.