The Serbian had earlier pulled out of Abu Dhabi exhibition and Qatar Open in Doha with elbow injury that has kept him out of action since Wimbledon previous year. Tiley further pointed out that Serena always want to give her absolute best and that she doesn't head into any event just to compete.
The 36-year-old was eight weeks pregnant last year when she triumphed for a seventh time at Melbourne Park to claim an Open-era record 23rd Grand Slam title. She won in 2003, 2005, 2007, 2009, 2010, 2015 and 2017.
There is also uncertainty over whether former champions Novak Djokovic and Rafael Nadal, the latter of which arrived in Melbourne earlier on Friday, will be fit to take to the court.
Williams past year beat older sister Venus in the final.
Williams is the latest big name to withdraw from the year's opening Grand Slam, which will be played from January 15 to January 28. However, Serena now said that she is not fully ready to return for the season-opening Grand Slam as she believes her preparations had fallen just short of what she needed to be competitive.
Novak Djokovic is finally set to return to action next week after six months out with an elbow injury and will then decide whether to take part in the January 15-28 Australian Open.
"The memory of last year's Open is one that I will carry with me, and Olympia and I look forward to coming back again", added Williams.
"I appreciate the support and understanding of my fans and everyone at the Australian Open".
"I've been in constant contact with Serena and her team and know this is why she has pushed it and pushed it until the eleventh hour to make her final decision".
Also in the mix will be No. 2-ranked Garbine Muguruza, last year's Wimbledon victor, U.S. Open champion Sloane Stevens and Venus Williams, who will be aiming to win her eighth major singles title at the age of 37.
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