(VIDEO) Major upset in Turin as Stefanos Tsitsipas forced to retire from Holger Rune tie and 2023 ATP Finals

Stefanos Tsitsipas was forced to retire from his match against Holger Rune at the 2023 Nitto ATP Finals in Turin, meaning the Dane won their clash in the Green Group.

The Greek player had just begun his third meeting with Rune when issues began to emerge. Prior to the start of the tournament, Tsitsipas had appeared to be struggling with elbow and shoulder problems but this seemed to have been resolved and he looked able to compete in his fifth consecutive ATP Finals.

The 25-year-old lost his first Group Stage match at the ATP Finals against Jannik Sinner in straight sets, 4-6, 4-6. However, he made a good start in his clash with Rune, getting a break point on the 20-year-old's first service game. Nevertheless, his opponent took it to a deuce. Although Tsitsipas won an advantage to give himself a second break point, Rune fought back again and was able to hold.

Tsitsipas then found himself in trouble as Rune got a 0-30 lead in the 25-year-old's first service game. However, he fought to equalize before pushing ahead. Although Rune then took the game to a deuce, Tsitsipas hung on and leveled the set at 1-1.

However, as Rune's next service game went on, it became clear that Tsitsipas was experiencing some problems, with commentators unsure as to whether the player was unwell or experiencing a back problem. A physio was called to the court and it became evident that this was not a situation that could be immediately resolved.

After talking with the physio for some time while his team watched on with worried looks, Tsitsipas was heartbreakingly forced to retire from the match. This meant that Rune got his first win at the ATP Finals after losing his opening battle with Novak Djokovic in three sets.

After Tsitsipas left the court, it was announced that the tournament's two alternates, Taylor Fritz and Hubert Hurkacz, would play an exhibition match that will begin shortly. Later today, Djokovic will face home player Sinner in their second match in the Green Group.

Meanwhile, Rune wished Tsitsipas well: "It was very unfortunate... we play a long season and it's important to take care of the body and I wish him all the best," he said. Rune will face Sinner in his last Group Stage clash, while in the unlikely event that Tsitsipas returns, he will play against Djokovic.