Well, in a 30 minute lesson it's hard to work on everything. I trust this coach, he has excellent credentials and has helped son a great deal. Another LHP on son's team does not have great mechanics but throws bullets... he has had arm injuries the past two years...I saw him pitch for the first time last week. Yup, he threw hard, struck out 5 to save game, but how long will his arm hold up? He's a senior and had to sit out half of his junior season and all summer due to injury.