The 2009 world champion admitted that he was not satisfied with progress during pre-season testing in Spain but is confident things will be different in Melbourne.
He cited the differences between Barcelona and Albert Park and the progress made late in the Barcelona test as reasons for not being too downbeat about McLaren's hopes.
This is despite admitting that McLaren could not have matched the top times seen in winter testing.
Asked if he was frightened by rivals' pace in testing, Button replied: "If we were racing in Barcelona this weekend, yes we would be, but it's different here.
"It's going to be cooler than it is now on Sunday, but it's still hotter than the test.
"It's a very different type of asphalt and we know it's a very different circuit to Barcelona.
"On the last day of testing, I got a much better feel for the car and we found something with the set-up, a direction and a feeling that I liked.
"But if you look at the testing times, there are certain times that we certainly could not have done."
Button is certain that McLaren will have a good understanding of the MP4-28 in Australia even though it did not throughout testing.
Components that played a part in its struggles have been removed and Button is confident that it will be possible to find a set-up that works well.
"The way that the car is here, we understand it very well," said Button.
"There are certain things that we have tried over the winter that we haven't quite got a handle on and those parts are not on the car.
"There are many areas we still need to improve and hopefully we can do some good set-up work and find something for the weekend that we like."
Although McLaren has struggled, Button is certain that starting the season with an aggressive new car design, rather than a more conservative evolution of last year's machine, will pay dividends.
While he downplayed fears that this path will put McLaren at a disadvantage in Australia, Button is certain that the team will make significant progress during the campaign.
"When you look at most cars, they are developed from last year whereas with ours it's very different," said Button.
"The geometry of the car is very different, the way the aerodynamics work is very different, so it is always going to be tougher if you have made bigger changes.
"We still don't think that should hinder us at the first race, but it should help us throughout the season having a much better development curve than most other teams."
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