You may be able to blow them away with speed the first time through the lineup, but the second time through, you really need to be able to hit your spots. What really helps is having that changeup after a steady diet of fastballs. I've always been in the camp of pitching to your defense and letting them make plays. K's are great, but if they're standing out there half the game not doing anything, when the ball is finally hit, they'll be caught on their heels.