Change look of post pages in same category

If I have a sports site, I can create a different category look for each team by creating a ‘category-#.php’ file. So now I can assign different ads to that category by changing the sidebar path. My question is … how do I do the same thing for the posts in that category?

I have an advertiser who wants to be a sponsor for Team A, and I can put him on the Team A ‘category’ page, but when someone clicks on a story about team A, those ads won’t appear. Can I change what appears on a ‘single post’ page based on the category it falls in?

Thanks.