McLaren's gamble on overhauling their car for the 2013 season looked to have backfired on Friday when they had a miserable day in the first two practice sessions at the Australian Grand Prix.

The British-based team won the last two races of last season but their cars were well off the pace at Albert Park with Jenson Button finishing 11th fastest in the second session - 2.386 seconds behind Red Bull's triple world champion Sebastian Vettel.

"We're 2.4 seconds off the pace, I'll be surprised, I'll be very happy if we're in the top 10," said Briton Button, the 2009 champion who has won three of the last four races in Melbourne.

"It's definitely not the place where we wanted to start the season but all is not lost yet. We're very good at turning it round.

I didn't think we were that competitive at the last test in Barcelona and I think I made that clear ... I still think we can improve the car a lot here,’’ he added. Most teams were satisfied to bring out an evolution of their 2012 challengers in the final year of the V8 engines before sweeping changes to the technical regulations come into force for next season.

The British-based outfit, however, went down a different design route and produced a chassis with significant changes. Team principal Martin Whitmarsh admitted they had contributed to a difficult day.

"It was one of the hardest days I can recall," he said. "We were lacking overall grip, consistency, understeer, poor ride. Very difficult day when we didn't go forward during the day, which is bit of a worry.

We made quite a conscious decision to make a lot of changes to the car for this season and we don't fully understand how to get the best out of it yet,’’ Whitmarsh added.