(CNN) For the third consecutive grand slam, Maria Sharapova has fallen to a first-round defeat. Now serious questions are being asked about her future.

The former world No. 1 was granted wildcard entry to the Australian Open but went down 6-3 6-4 to Croatia's Donna Vekic off the back of an injury-ravaged 2019.

Sharapova will fall out of the top 350 when the latest world rankings are released after the tournament, admitting she wasn't sure whether she would play in Melbourne again.

"It's tough for me to tell what's going to happen in 12 months' time," said Sharapova, who won her only Australian Open title in 2008.

"I was fortunate to get myself to be here and thankful to (Tennis Australia boss) Craig (Tiley) and the team for allowing me to be part of this event."

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