2016 This should be a great place to come with your question, not the library as some might suggest. I hope you will find this to be a great resource for a long time to come. By definition "nit-picking" is a small minor detail which I think perfectly frames your question acknowledging that your son is still getting some playing time. I think it is perfectly natural and wise to wonder why a role change takes place. You have received some great advice already. Mine would be mostly about communication and effort. Your son should let the coaches know of his goals and desires by word and action. His hitting skills are obviously appreciated. Keep working on those but figure out what else is needed, i.e. foot-speed, quick first step, or tracking fly balls....
“Some” know what they’re talking about.