The Formula One teams wrapped up pre-season testing in Bahrain earlier this month with Hamilton on top of the timesheets and his team looking clear favourites to win at Albert Park on Sunday.
With constructors' champions Red Bull and other teams still grappling with the new turbo-charged hybrid engine, rival drivers at Albert Park added fuel to the fire by tipping Mercedes to cross first in Melbourne.
Felipe Massa, who will race with Williams this season after a long stint at Ferrari, went so far as to tip them to win the constructors' championship, but Hamilton was having none of the cheek.
"Everyone's talking us up and predicting the future but we really can't say what's going to happen this weekend," the Briton told reporters on Thursday.
"We know we'll be strong, we've not left any stone unturned, we've done absolutely everything we can possibly do, so we're hoping we'll be at the front, that's our goal. But we can't say that's going to be the case.
"Coming here, knowing that this is the best chance out of all the years, I don't know; I haven't even got in the car and gone on the track yet."
The 29-year-old finished fourth in the championship last year, with his German team mate Nico Rosberg sixth, propelling Mercedes to second in the constructors' race behind Red Bull ni his first season with the Silver Arrows.
Hamilton became the youngest Formula One world champion in 2008 when driving for McLaren, a record since taken by Sebastian Vettel in 2010, and has been installed by some bookmakers as favourite to win a second title, breaking the German's four-year reign with Red Bull.
"It is a long, long time since I won the world championship - it feels like a lifetime ago - but I'm still here, still motivated and actually a lot more than I ever was before and more focused than I ever was before," he said.
"If the package is there then we will do the job and there's no reason why we can't be at the front again."
Although feeling confident of Mercedes' preparations ahead of Sunday's race, Hamilton was less than effusive about the new V6 engines, the biggest shake-up the glamour sport has seen in decades.
"Naturally, I think, I probably speak for all of us that last year's car felt better," he told reporters at Albert Park.
"It was perhaps a little nicer to drive. We had lots more downforce. That was a car that was in its fourth year of evolution.
"Now we're in a new phase and it's something that just takes some time to get used to. The sound, for example, is not as impressive as we had in the past, but once you get all the cars on the track, I'm pretty sure it will be impressive as well."
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