Sydney, Australia, 9 January 2013 | AAP

Bernard Tomic has delivered a serving masterclass that he believes has put every one of his rivals on notice days out from the Australian Open.

The bulked-up Tomic rocketed down 14 aces in 10 service games and landed 74 per cent of his first deliveries in a 7-6 (4) 6-2 second-round shellacking of German nemesis Florian Mayer at the Sydney International.

It was a clinical performance that left Mayer – who had beaten the 20-year-old in all three previous meetings – feeling helpless at Ken Rosewall Arena.

“After the match, he said: ‘You’re serving unbelievable. Nothing I could do,'” Tomic said.

“It’s good to hear that from all the players I’m playing. There is talk now that I’m serving really good and my groundstrokes are really good, too.

“I’m moving really well. There is nothing much more I can ask myself at this stage.”

World No.1 Novak Djokovic said something similar to the Australian after also copping a straight-sets drubbing from Tomic at the Hopman Cup last week in Perth.

Tomic is now a perfect five-from-five this summer and into a quarterfinal in Sydney against defending champion Jarkko Nieminen.

The two-time former grand slam junior champion puts it all down to his new monster serve and improved attitude and work ethic.

“I put a lot work in in strengthening my shoulder up, and now 90 per cent is still really at 200kph,” he said.

“I’m serving consistently at 190 and hitting my spots, so there’s nothing these players can do.

“(I have) a lot more strength in my upper body and it’s important to be flexible as well – I’m getting much more angle in the court.

“It’s not about how hard you hit the serve. I’m acing a lot of guys at 150, 160 out wide because I’ve got one of the lowest trajectory serves that hits that deuce corner.

“I love serving like that. Even if they get it back, you’ve got the whole court to do anything you want with the shot.

“So the serve is really my key where I’ve changed everything probably the last few weeks, as well as my attitude.”

With American world No.13 John Isner among four seeds to crash out on Wednesday, Tomic is now a warm favourite to claim his maiden tour title in Sydney.

Fellow American Ryan Harrison eliminated top seed Isner 6-4 6-4 before Isner revealed he may have to withdraw from the Open starting on Monday due to a knee injury.

Harrison will face Julian Benneteau in his Thursday quarterfinal after the Frenchman advanced when Czech sixth seed Radek Stepanek retired four points into their second-round match with a back injury.

Italian third seed Andreas Seppi beat Australian wildcard John Millman 6-2 3-6 6-3 to book a quarterfinal with Spanish eighth seed Marcel Granollers, a 6-2 7-6 (4) winner over Italian Fabio Fognini.