Defending champion Serena Williams has withdrawn from the Australian Open, saying she is not ready to return to tournament tennis.

Williams was pregnant with her first child when she won last year’s tournament at Melbourne Park, her 23rd Grand Slam singles title of her career.

She gave birth to her daughter, Alexis, in September.

She played in an exhibition tournament last week in Abu Dhabi and indicated after her loss to French Open champion Jelena Ostapenko that she might not make it to Melbourne.

“After competing in Abu Dhabi I realized that although I am super close, I’m not where I personally want to be,” Williams said in a statement released Friday by Australian Open organizers.

“My coach and team always said ‘only go to tournaments when you are prepared to go all the way’. I can compete – but I don’t want to just compete, I want to do far better than that and to do so, I will need a little more time.

“With that being said, and even though I am disappointed about it, I’ve decided not to compete in the Australian Open this year.”