Former world number one Venus Williams has withdrawn from the season-opening Brisbane International after suffering an “unexpected setback” in training.

The 39-year-old, who won the last of her seven Grand Slam singles titles in 2008, hopes to play in Adelaide before the Australian Open on 20 January.

A replacement for the world number 52 will be announced on Thursday.

World number one Ashleigh Barty and Australian Open champion Naomi Osaka are among a strong field.

The tournament begins on 6 January.