The Danish tennis star say that he is suffering from back trouble.
"My back has gone into spasms, but fortunately, scans have confirmed that it’s nothing serious. So, it will be 2–3 days of rest. It’s just really annoying and the timing is unfortunate," the Dane writes.
The Danish tennis player had actually received a wildcard for the tournament in Belgium.
It has been only a month since the tennis star made his comeback, following a ruptured Achilles tendon sustained during a match in Stockholm last October.
Since then, the Dane has competed in two ATP tournaments—in Shanghai and Tokyo—but was eliminated in the first round on both occasions.
Holger Rune made his return to the Davis Cup when he played for Denmark in Hillerod.
The Dane’s next tournament is expected to be the ATP 500 event in Basel, Switzerland, which begins on 26 October.