MONTREAL, Canada - Jenson Button was a long-shot winner of 2011's Canadian F1 GP and the McLaren driver will be rolling the dice again on Sunday after qualifying 10th with a tyre strategy at variance to that of rivals.The Pirelli tyres have been a key factor in this the most unpredictable of seasons with teams struggling to get to grips with new regulations and compounds.DECISION A GAMBLEGearbox problems during Friday's practice sessions left Button playing catch-up so the Briton was the only runner in the final qualifying session to use soft rather than supersoft tyresHowever the decision looks like a gamble with very hot weather expected for the race, "We're starting with a different tyre from everyone else," the 2009 F1 champion told reporters. "I don't know if that's a good or bad thing but it is what it is. It's going to be very hot and perhaps that will throw it up in the air a little 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 or more laps. That could make a one-stop strategy possible while most teams are likely to go for two.ANOTHER BATTLEButton made six in his epic 2011 fight-back 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 win.He'll has another battle on his hands on Sunday if he is to score big points after a slump in form since the Australian season-opener.McLaren team principal Martin Whitmarsh said on Saturday: "These tyres are quite difficult to get the temperature in and working. It's a very fine window, clearly a lot of teams, including us, are finding it a bit of a challenge."We're still learning."