Defending champion Jannik Sinner stretched his indoor hard-court winning streak to 29 matches with a 6–3, 7–6 (3) victory over American Ben Shelton in a low-stakes round-robin encounter at the ATP Finals in Turin on Friday.

The atmosphere inside the Inalpi Arena was noticeably relaxed, with Sinner already assured of finishing first in the Bjorn Borg Group and booking a semi-final meeting with Alex de Minaur, while Shelton’s losses in his opening two matches meant he was already out of contention.

Sinner broke Shelton in both the first and last games of the opening set. The American couldn’t convert a break point at 2–1, while Sinner repeatedly pulled out clutch serving when needed, firing two aces in that game alone to hold.

“Serving well in the big moments has really helped me this season,” Sinner said. “If you want to come here and win all three round-robin matches, you have to play at a very high level — and that’s what I’ve managed to do.”

Shelton produced a stronger challenge in the second set, holding to love three times and saving a match point at 5–4 before forcing Sinner into his first ATP Finals tiebreak in two years. But the Italian raised his level once more to close out the match.

“When he cracks a huge serve, there’s not much you can do — you just have to accept it,” Sinner added. “Mentally, I’ve been in a great place so far. Now we’ll see what comes next.”

Making his ATP Finals debut, Shelton had previously fallen to two-time champion Alexander Zverev and Canada’s Félix Auger-Aliassime. Those two were set to meet later on Friday in a winner-takes-all showdown for a spot in the semi-finals against Carlos Alcaraz.

Sinner’s hopes of finishing the season as world No. 1 disappeared on Thursday when Alcaraz completed a perfect run in the Jimmy Connors Group by beating Lorenzo Musetti. That left Sinner playing for little more than pride — and his unbeaten streak — against Shelton.

Before the match, Alcaraz was presented with the ATP year-end No. 1 trophy on court, an honour Sinner claimed last season. The pair could still face off one more time this year if both reach Sunday’s final.

“It’s a pleasure to be the world No. 1 — something I work incredibly hard for,” Alcaraz said. “It’s a huge achievement and I’m really proud and happy.”