MONTREAL, June 9 (Reuters) - Jenson Button was a long-shot winner in last year's Canadian Grand Prix and the McLaren driver will be rolling the dice again on Sunday after qualifying 10th with a different tyre strategy to his rivals.
The Pirelli tyres have been a key factor in the most unpredictable of seasons, with teams struggling to get to grips with new regulations and compounds.
After gearbox problems during Friday's practice sessions left Button playing catch-up, the Briton was the sole runner in the final qualifying session to use the soft tyre rather than supersoft.
With very hot weather expected for Sunday's race, the decision looked a gamble.
"We're starting with a different tyre from everyone else, I don't know if that is a good thing or a bad thing but it is what it is," the 2009 champion told reporters.
"We will see tomorrow, it's going to be very hot and hopefully that will throw it up in the air a little bit and we won't be quite sure what the tyres are going to do.
"Taking a little bit of a punt (gamble) I suppose, which I think you have to do when you're that far back and you can still have a good race from there tomorrow."
The big question will be the level of degradation of the compounds, with the supersoft holding up better than expected and likely to be good for 30 laps or more.
That could make a one-stop strategy possible while most teams are likely to go for two.
Button made six last year in an epic fightback in the wet from the rear of the field at a re-start to overtake Red Bull's Sebastian Vettel, again on pole on Sunday, on the final lap to steal the victory.
He has another battle on his hands on Sunday if he is to score big points after a slump in form following his win in the Australian season-opener.
"These tires are quite difficult to get the temperature in and get them working," said McLaren team principal Martin Whitmarsh.
"It's a very fine window, clearly a lot of teams, including ourselves, are finding it a bit of a challenge. We're still learning." (Reporting by Steve Keating, editing by Alan Baldwin)