Serena Williams has withdrawn from her Yarra Valley Classic semi-final against world number one Ashleigh Barty with a right shoulder injury.
Williams had earlier beaten fellow American Danielle Collins 6-2 4-6 10-6 in the last eight in Melbourne.
Williams will be seeking a record-equalling 24th Grand Slam singles title at the Australian Open.
Serena Williams Withdraws From Australian Open Semi-Final Against Ashleigh Barty Over Shoulder Problem https://t.co/UJtzVTFiSs
— Agent 47 (@LifeOfUzy47) February 5, 2021
The first Slam of the year begins on Monday and all six ATP and WTA warm-up events are being held at Melbourne Park.
Williams, 39, won her last major title at the Australian Open in 2017. She missed the 2018 competition and reached the quarter-finals in 2019, but fell in the third round last year.
Barty will play either Garbine Muguruza or Marketa Vondrousova in the final.
Spain’s Muguruza thrashed Australian Open champion Sofia Kenin 6-2 6-2 in a rematch of last year’s final.
The USA’s Kenin made 28 unforced errors and left the court in tears after the 77-minute defeat.
Czech Vondrousova beat Nadia Podoroska of Argentina 3-6 6-3 10-4.
Third sets in the WTA are being played over a 10-point super tie-break following the delay to the tournaments because of Covid-19 testing.