I am not a sports person, so I have no idea, but I suspect they'd be cheered on. Unless they were seen as part of an enemy team. I think people feel a sense of pride in the people that play on local teams. My imagination says that might go something like this: "That guy's probably eaten some of the hotdogs from the factory I work in. I probably played some small part in this famous guy's awesome sports abilities somehow."

I'm really itching to do an experiment now. (: Maybe I will...