World number six Novak Djokovic has pulled out of Serbia’s Davis Cup first-round qualifying tie due to injury, the country’s tennis federation (TSS) said.

Djokovic, who was set to represent Serbia in their Jan. 31-Feb. 2 meeting with Denmark in Copenhagen, retired due to a hamstring injury in his Australian Open semi-final match against Alexander Zverev last week.

The 24-times Grand Slam champion was booed by the crowd at Melbourne Park and he responded by posting a photo of an MRI taken of his left hamstring with the caption:

“Thought I’d leave this here for all the sports injury ‘experts’ out there.”

Djokovic takes aim at injury ‘experts’ after sour Australian Open exit

Djokovic, 37, was part of the Serbian team which lifted the Davis Cup in 2010 following a memorable victory over France in Belgrade.

“We are weakened by not playing Novak, but we are still going for the win. The Danes have a great player in Holger Rune, but our players are also great and I believe in my team,” Serbia captain Viktor Troicki said.