McLaren driver Jenson Button has tipped rivals Mercedes and Williams to be the leading lights as the Formula 1 season kicks off on March 14th.

Speaking of his own team, the Briton said McLaren can only guess how good their new car is after winter testing.

Although they did not set the world alight at the final pre-season test in Bahrain, the 2009 World Champion feels confident his car can be competitive.

The first Grand Prix of the year is in Melbourne in a week and a half and Button told Sky Sports News, two teams have stood out in particular.