Holger Rune's ex-coach Patrick Mouratoglou has reacted to news of the player's back injury forcing him to retire from his opening match against Mackenzie McDonald at the Cincinnati Open.

World No. 5 Rune retired in his first match at the Western & Southern Open in Cincinnati due to a back injury. The Dane was trailing 4-6 0-2 at the time and took the decision to withdraw from the tournament ahead of the US Open.

Rune turned out to be one of many players retiring from their matches due to injury, as the next few days saw the combined ATP and WTA 1000 event lose Elena Rybakina, Alejandro Davidovich Fokina, Donna Vekic, Dusan Lajovic, and Marie Bouzkova this way, as well as Rune's Round of 32 opponent McDonald.

Mouratoglou, who coached Rune from October 2022 until April 2023, posted a message of sympathy and support to the player on Instagram following his withdrawal.

"Back injuries are very paralyzing. You can’t move well and feel pain every time you hit a shot.

"I know how it feels as I suffered from it for 6 months this year. I feel sad for @holgerrune because he was very excited to do well in @cincytennis. The positive thing is that in his case, it should heal fast. Let’s move past this and get ready for the @usopen," he wrote.

The 20-year-old has previously spoken of his inspirations and motivations to continue in the sport.

One huge inspiration for him is his compatriot Caroline Wozniacki, who returned to the sport this summer after three years, during which time she gave birth to two children.

"It was very inspiring to watch a Danish player win a Grand Slam, no one from our country was there succeeded before and seeing her triumph made me believe that I can do it too," he said.

Moreover, Rune spoke of simply wanting to achieve his goals.

"I have my goals that I want to achieve and have chances to achieve it this year also and I'm going to go for it," he said.