I share your concern, but I am not sure concern is necessary. DD had a biology test yesterday (first time with this class). She was nervous about the test, so I was nervous for her. When I got home from work the first thing I asked was "how was the test?". Her response "aced it!!". I was thrilled for her. So then why does hoping for success on the field need to be a concern? In my opinion we just want to see our children do well and be happy. If that is a bad thing, then I guess I will need to live with it. That said, I do understand that this can become unhealthy depending how far it is taken.
Your last sentence nails it. Rooting for your kid is normal. Just don't take it too far.
I hope he knows he has a Braves A for the tat...
...When people ask me why I spend so much time and money on softball I tell them I don't. I spend my time and money on my daughter.