Use your best, and pray. I mean, you already won your league... Most probably you'll end losing 6-0 or something like that, but you never know :P.

i.e. a friend of mine is lv 13, played a friendly against me (I'm lvl 2) and barely won 1-0 ET (90' ended 0-0). I wasn't even watching, and was my B team lol.

Maybe you have 1% chance, but who cares :P. Maybe is just you lucky day xD