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 January 31-February 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, 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.

England dismiss Pakistan for 110 to seize control of Lord's test
Raphinha, Fermin score as Barcelona beat Athletic in home opener
Celtic and Rangers to play cup match behind closed doors after pitch invasion
Chelsea and Fulham reach League Cup third round as Welbeck scores on debut
PSG to meet Barca, Man City as Champions League draw throws up marquee ties