The mighty Nadal has been swept out of the Wimbledon Tennis Tournament in straight sets by an unknown in the first round. Yes he has had some injuries lately, but he has been dominating clay court play for months. He could fairly point out that tennis on grass is a remarkably different sport than tennis on clay (or concrete).
Think how shocked we would be if a professional basketball team announced that they were changing the surface of their floor from wood to cement and were also going to raise their rim by six inches. We expect consistency in the conditions of basketball, ice hockey and bowling, but not tennis.
Is there a sport that allows as much variation in the game under the same name? The only one I could think of is baseball, in which a stadium can have artificial turf versus grass and the outfield fences can be arranged in a variety of ways.
Are there other examples of sports that are really multiple, different versions of a game? And are any of them as variable as is tennis?