Novak Djokovic was beaten by Alex de Minaur as Serbia lost to Australia in the United Cup quarter-finals.
It was the Serb's first defeat in Australia since 2018 and comes 11 days before he begins the defence of his Australian Open title from 14 January.
Ajla Tomljanovic beat Natalija Stevanovic in the second match of the tie to secure Australia's victory.
They will meet Germany or Greece in the last four.
Djokovic needed treatment on a wrist issue during Serbia's victory over Czech Republic on Tuesday and had more treatment before world number 12 De Minaur broke serve late in the first set.