Rafael Nadal has withdrawn from the Brisbane International with an ongoing knee injury but says he still intends to play at the Australian Open.
The world number one had already pulled out of the Mubadala World Tennis Championship in Abu Dhabi this weekend.
"I am still not ready after last year's long season and the late start of my preparation," said Spaniard Nadal, 31.
Meanwhile, Roger Federer does not "think it's normal and realistic" to match his 2017 exploits next year.
The 36-year-old Swiss, who has arrived in Australia to play in the Hopman Cup in Perth, won the Australian Open and Wimbledon in 2017.
"I've got to try and keep it cool. Try my best and see what happens but the preparation has been good so far," he added.
"We'll see how things go."
The Australian Open starts on 15 January and Nadal, who was beaten by Federer in a five-set epic in the 2017 final, is planning to arrive at the start of the month.
"I will be seeing my Aussie fans when I land on the fourth in Melbourne and start there my preparation for the Australian Open," he said.
Britain's Andy Murray, who has not played a competitive match since Wimbledon because of a hip injury, is still aiming to make his comeback in Brisbane next week as part of his own build-up to the Australian Open.
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