This is a huge issue I am sure for many coaches such as myself. Who do you play and when do you play them? At the Varsity Baseball level I am finding out that you can not please everyone. Unfortunately you only have 9 positions on a Baseball field and with 16 kids on the team, well you do the math.
I do appreciate the fact that everyone wants to play and get in there to contribute. It is better to have some rumbles and grumbles because it means they care and they know they can help the team win if they get the chance. It just so happens to be one of the hazards of coaching, not that you have to break a kids self esteem but tell them that some may not play everyday. When you give them the chance, you hope they embrace it and do the best they can to help your team win in that current situation.
Coaching is a lot harder than some people may think. A good coach is aware of all aspects of the game both mentally and physically. To coach the mental side is one task that can be harder for some but it is very necessary if you want the most out of all your players.