Holger Rune withdrew from the Plava Laguna Croatia Open Umag due to a lower back injury on Friday, the tournament announced.
“Unfortunately I won't be able to play at the Croatia Open this year, as I have issues with my lower back, an injury that prevented me from performing at my usual level this week,” Rune said. “Starting from Monday, I will undergo the necessary treatments and then take some rest."
The 20-year-old Rune, who boasts a 37-13 season record, earned his fourth tour-level title this year in Munich. He was also a finalist at the ATP Masters 1000 clay-court events in Monte-Carlo and Rome.
A quarter-finalist at Wimbledon, Rune is aiming to make his Nitto ATP Finals debut this season. The Dane is seventh in the Pepperstone ATP Live Race To Turin.