The next time you watch a college game, take a look at the starters. Everyone of them was a stud at some point in their career. Now, take a look at the bench. Everyone of them was a stud at some point in their career. That starter had better understand that with the next recruiting class, the coach has done his best to recruit someone better than him. That's the facts. My daughter is a junior. They have recruited several players to take her position. She understands that if she does not produce they will take her spot. College coaching is tough. They work hard to do team bonding but then again, every player knows that every other player on that team is battling for 9 starting spots.
Part of that is because of turnover. Coaches can't just assume that kids they bring in as freshman will be around for 4 (or even 3) years. Kids change schools all the time....baseball related or not. No coach can possibly bring in a kid and say "You'll start all 4 years and I won't recruit anyone else". Coaches are there to win. If you're the top player you'll play....but as CoachB said, it's the coaches job to bring in the best of the best every year. If a kid is starting this year...and the coach finds someone better to bring in next year he'd be crazy not to do it. Tough spot for both the kids and the coach, but when your job depends on winning, you've got to do what you can to make sure that happens.