Bernard Tomic has all but declared Novak Djokovic unbeatable ahead of next week's Australian Open.
Djokovic is a hot favourite to follow up his extraordinary 2015 season with an unprecedented sixth men's Open triumph in Melbourne.
The Serbian juggernaut collected 11 titles, including three majors, and went within one match of completing the first calendar-year grand slam sweep since 1969 in amassing a record $US21,592,125 ($A30.92 million) in season earnings.
Any hopes his challengers may have had of Djokovic easing up in 2016 were blown away when the world No.1 crushed Rafael Nadal for the loss of three games in the Doha decider last week.
A shellshocked Nadal claimed Djokovic had taken tennis to unseen levels and Tomic on Wednesday night couldn't disagree.
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"Novak, it's just a joke now. It's amazing what he's doing. That's the reason why he's the best player in the world," Tomic said after powering into the Sydney International quarter-finals with a 6-2 6-4 win over young countryman Jordan Thompson.
"I think even Roger and Rafa are just ... when you step on the court against Novak now, it's like: `How can you beat him?'
"Even Rafa playing that final in Doha, it was amazing tennis to watch, but so comfortable, and on score just shows how much Novak is dominating the sport.
"I think he is a different level, Novak, now, and there is a reason why he's there.
"I think the other players, there are a little bit more weaknesses and stuff.
"There is a reason why Novak is the best; no weaknesses. I can't think of any. He deserves to be there."
Tomic, at a career-high No.17 in the world, said Milos Raonic's victory over Federer in last week's Brisbane International was also a "good sign for us" challengers.
"Milos winning that tournament, it gives us confidence stepping on the court against Federer, Murray, and against these other guys ... except Novak," Tomic said.
