If you don't play young players like Gilaspie against lefties how can you ever expect them to learn how to hit them. If you keep telling them that they can't hit lefties and that player X will play in their place each time you will eventually ruin their confidence.
See BA for an example - maybe not the very best example I'll admit, but he came into the team as a much vaunted prospect and had his confidence shattered by Ozzie as he was never allowed to settle and grow into his position.
You have to let young players go out and learn their craft, they don't come into the game as All Stars. They will make mistakes and struggle at times but at the end of the day you will hopefully get a player that's worth having.
It's called player development - just about every other ball club understands this.
Sadly we seem to be all about the quick fix. I'm not saying we need to go totally young - I'm saying we need a blend of youth and experience, but we need to give the youth a fair chance to flourish.