HALLE, Germany — Top-ranked Jannik Sinner was upended by Alexander Bublik 3-6, 6-3, 6-4 in the second round at the Halle grass-court tournament Thursday.

Sinner, the Halle defending champion, was playing in his first tournament since losing a five-set thriller to Carlos Alcaraz in the Roland-Garros final.

The three-time Grand Slam champion had beaten Yannick Hanfmann in the first round this week, but the big-serving Bublik gained some revenge after having lost to Sinner in the quarterfinals in Paris.

“It’s a special one – I had never beaten the top one (No. 1) in the world, that’s an accomplishment,” Bublik, who is ranked 45th, said in his on-court interview.

The Kazakhstan player recorded 36 winners and 15 aces against the top-seeded Sinner in the Wimbledon warmup tournament.

“I just kept serving, kept putting him in uncomfortable positions and it worked well,” said Bublik, the 2023 Halle champion who will face Tomas Machac in the quarterfinals.

Also Thursday, the second-seeded Alexander Zverev outlasted Lorenzo Sonego 3-6, 6-4, 7-6 (2) to reach the quarterfinals.