I have never read anywhere that if you shoot in RAW that altering the white balance will affect the picture quality. Anyway, if I shot a match then I would look at the photos more for content than absolutely accurate white balance. On a typical grey overcast day the setting cloudy will not be a million miles out! The exact colour balance will shift as the full 90 minutes progresses anyway, possibly from moment to moment, there is no way that you could keep checking the W/B. The goal would happen at the wrong moment and you would miss it! Surely the use of the expo disc or similar is for the considered shot in tricky lighting condition, say mixed natural/artificial lighting like an interior lit by tungsten or strip lighting and daylight. That could be very useful to give a correct reading but for maximum quality you would still shoot in RAW and maybe change the W/B off the correct setting to give the atmosphere you want. Don't get me wrong, I agree that in general terms it is better to get things right in camera but the expo disc is only a guide and starting point and not necessarily a good idea for fast moving action, in shade one second bright sunshine the next!
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