Rune and Tsitsipas squared off in the second group-stage match at the ATP Finals in Turin on Tuesday in a pivotal match. Both players lost their opening matches to kick off the tournament and sought a first round-robin.
Rune, who is making his tournament debut having qualified for the first time, was a slight favorite going into the match after a fantastic run of results in his last two tournaments following the appointment of Boris Becker as his new coach.
Tsitsipas, for his part, arrived on the scene with doubts regarding his elbow. He had reportedly stopped practicing for a couple of days before the tournament started, although he allayed such fears following his defeat to Jannik Sinner on Sunday. But Tsitsipas' body let him down on Tuesday afternoon.
Just three games into the contest, the 2019 champion was physically in a spot of bother and he retired on the first changeover after consultation with the ATP physio. The crowd inside the Pala Alpitour did not take kindly to the Greek throwing in the towel after just a few minutes and started to boo him.
After the match, Tsitsipas apologized to the fans and revealed that he had been struggling with a back injury. And despite being given the "green light" by the doctors to compete, he felt "terrible" and was noticeably moving gingerly and his serve was far from perfect.
Aside from the crowd's disapproval inside the stadium, tennis fans on social media criticized the Greek for playing with a known injury when he could have withdrawn and reserved his spot for an alternate. Rune, however, was sympathetic to his opponent and defended him in a tweet on X.
"We are not in Stefano's body. So we cannot comment on what he should have done. We are here to fight and win. No one here in the top 8 is a quitter and we will try to the end. If we only thought rationally, we wouldn't be where we are today."