Defending champion Maria Sharapova and top seed Simona Halep have withdrawn from the Brisbane International due to injury.

Sharapova sensationally pulled out of the tournament just hours before her opening-round match on Tuesday against Russian compatriot Ekaterina Makarova.

The five-time grand slam winner said she had a left forearm injury and didn’t want to risk any further damage ahead of this month’s Australian Open.

“I hurt my forearm in practice a couple days ago and need to precautionary withdraw with the Australian Open starting in just a matter of time,” Sharapova said.

“This is such a special event for me especially being the defending champion. I’m looking forward to seeing all my fans in Brisbane next year.”

World No.2 Halep then announced her own withdrawal less than an hour later due to a left leg injury.

Halep was set to face two-time Australian Open winner Victoria Azarenka in a second-round match after being granted a first-round bye.

It’s unclear at this stage if the Romanian will play in the upcoming Sydney International.

Sharapova will head straight to Melbourne to continue her preparations for the Australian Open.

A forearm injury forced her out of a tournament in Japan in October but she managed to play the WTA Finals and the Fed Cup final for Russia.

Sharapova’s withdrawal means if Agnieszka Radwanska avoids an early elimination in Shenzhen, the Russian is likely to lose a top-four seeding at the Australian Open.

A lucky loser will be named to play Makarova later on Tuesday on Pat Rafter Arena.