What can I say to my crush on facebook? Please help!?

Okay so there is this guy on my brothers baseball team that I REALLY like. I like him more than any other guy I have ever liked. My brother already knows and he is fine with it. I have limited time to get to know him because there are only 2 more tournaments left and I dont know if he is playing next year. There are some practices that I go to, though. Anyways he is really shy and I think he likes me too. I always catch him looking at me when I look at him and he smiles at me sometimes. One time I gave him a thumbs up when he was playing and I think he saw me. Everytime something funny happens he always looks at me but I can tell he is really shy around girls. So to start things off, I send him a message on facebook after a game and was like "Hey you played really good at the games today" and he responded back the next day just "thanks" and I was like "your welcome (:". So far he hasnt replied. I think he is really shy and doesnt want to mess things up. What can I say to him that wont make him think Im like stalkerish. Something that might make it sound like I HAVE to message him (like a question or something). I really cant mess this up, I like him way to much and In a few weeks it may all be over unless I can get him to open up. I know he likes me, I just have that feeling that I never got with any other guy before.