Holger Rune will be credited with his first win in the Green Group after Stefanos Tsitsipas was forced to retire due to a medical reason after just three games of their Nitto ATP Finals round-robin match Tuesday afternoon in Turin.

The 20-year-old Dane lost his first match on debut against Novak Djokovic but is now 1-1 in Green Group play after the Greek was forced to retire after just 15 minutes inside the Pala Alpitour with Rune leading 2-1.

“For me, it’s important to be fit and feel good with my back. The pain was very big,” Tsitsipas said following his retirement due to a back injury. “I’ve gone through pain during matches in the past, and I endured pain, but this was clearly too much to handle. I had to take the difficult decision to do what I did.

“I felt it at the second game of the match. I actually felt it in the warm-up with my serve. Warming up on my serve, I felt very irritated and lots of pain hitting me on my back. I kind of knew at that time that I might not be able to go all the way.”

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Earlier this year Rune reached quarter-finals at Roland Garros and Wimbledon and won the title in Munich. He will face Jannik Sinner in his final round-robin match on Thursday. The Italian Sinner plays Djokovic on Tuesday evening.

Alternates Taylor Fritz and Hubert Hurkacz will now play an exhibition one-set match. Both have competed at the Nitto ATP Finals before, with Hurkacz qualifying in 2021 and Fritz in 2022.

Tsitsipas lost against Sinner in his opening match. The 2019 champion lifted his only tour-level trophy of the season in Los Cabos.