I love basketball, but I haven't played on a team until now. I've been playing piano for 7 years (I'm not serious though, just for the fun and experience), and now I want to join a basketball team but my friend told me that if you sprain your finger, break it or something, then I can't play piano anymore.
Hmm.. Go on playing basketball. I am a pianist too and i even an enthusiast on playing sports like basketball, volleyball, badminton tennis and etc. Another example, take a look on Jay Chou(Taiwan's finest artist and he's known all around Asia). Jay is a pianist and he's been playing piano for more than 25 years. He started to play piano at the age of 3 and now he's 29(or 30, i can'r remember). You can check him playing the piano here: http://www.youtube.com/watch?v=cbSeZh6apVk Jay is the one with the black coat.
On the other hand, Jay Chou is also a great basketball player. Basketball is his most favorite game(read about him in Wikipedia). You can see him playing basketball with some tricks on a small clip of the movie "Kung Fu Dunk". Here's a link: http://www.youtube.com/watch?v=vPYxpg9CTAo He is the guy at 00:10.
Indeed, "prevention is better than cure" but it doesn't mean that you can't learn basketball because your a pianist. Because, for those who never try to learn will never learn. Once you've got your desire(in you case, playing basketball), this can bring happiness and satisfaction to yourself plus it adds self-confidence! Trust me. Just BE CAREFUL.