Nico Rosberg won the Australian Grand Prix by 26 seconds and while both Button and McLaren teammate Kevin Magnussen finished on the podium, the 2009 world champion is not expecting the Woking-based constructor to challenge for the win.
He was quoted by The Mirror as saying: "We have good upgrades coming for Sepang but I don't think that will be enough to challenge Mercedes.
"But if it puts us in the gap between them and the rest that's good news.
"We are here to fight for the championship. I don't know when a win will happen but that is what we are working towards."
McLaren currently lead the team standings, eight points ahead of Mercedes.