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."
The world No 6 did not appear to be serving at 100% in the second game, and his movement was noticeably laboured as he returned in the third.
The 25-year-old called the ATP physio during the changeover, and after a conversation, decided he could not continue and retired, leading to boos from the Italian crowd. An exhibition set between alternates Hubert Hurkacz and Taylor Fritz was then played to offer spectators some more action.
There had been reports of Tsitsipas cutting practice sessions short at the event due to an injury, but he took to the court for his opening match against Jannik Sinner on Sunday, which he lost 4-6, 4-6.
