Serena Williams has withdrawn from her Yarra Valley Classic semi-final against world number one Ashleigh Barty with a right shoulder injury.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.
Australian Barty, who won 7-5 2-6 10-4 against American Shelby Rogers, has received a walkover into the final.
Williams will be seeking a record-equalling 24th Grand Slam singles title at the Australian Open.