PARIS — Stefanos Tsitsipas qualified for the ATP finals by beating Alexander Zverev 7-6 (2), 6-4 in the third round of the Paris Masters on Thursday.
Jannik Sinner, meanwhile, pulled out of the tournament because of some questionable scheduling.
The seventh-seeded Tsitsipas earned his first win over a top 10 player this season, hitting 37 winners to 28 for Zverev.
The Greek took a 3-0 lead but failed to serve out the first set at 5-3 by sending a backhand into the net.
In the tiebreaker, Tsitsipas capitalized on two consecutive forehand errors from Zverev to lead 5-2 before taking the first set with an ace.
Tsitsipas broke Zverev in the opening game of the second set and clinched the victory with his 10th ace.
Zverev can still qualify for the ATP finals but now depends on the results of other players.
Alex de Minaur and Hubert Hurkacz stayed in contention for the two remaining spots at the eight-man tournament that will be played in Turin from Nov. 12-19.
Before the Paris Masters, Novak Djokovic, Carlos Alcaraz, Daniil Medvedev, Sinner and Andrey Rublev had already qualified for the ATP finals.
De Minaur, who got a walkover into the quarterfinals after the fourth-seeded Sinner withdrew, will next play the fifth-seeded Rublev, who ousted qualifier Botic Van de Zandschulp 6-3, 6-3.
The 11th-seeded Hurkacz beat Francisco Cerundolo 6-4, 6-3 to next face Grigor Dimitrov, who cruised past Alexander Bublik 6-2, 6-2.
Karen Khachanov, who won the tournament in 2018, rallied to beat qualifier Roman Safiullin 4-6, 6-4, 6-2 to set up a quarterfinal match against Tsitsipas.