i have only just bought some rubber mats for the very same reason, so i dont know yet how they will work out or how they will last the winter. to be honest they ended up being quite expensive as i needed a good few of them. very typically, only AFTER i had bought them, someone made the much cheaper suggestion of using old carpet. the only downside being that the grass wont grow up through it during the summer, but if it is a really really muddy patch you probably wont get too much grass growing there anyway during the summer. now why didnt i think of that??