There is a trend within the MLB to go away from the windup. If you break down the mechanics of throwing a baseball hard there is no logical reason to have to throw from the windup. The primary reason for the decrease in velocity from the stretch (with runners on) comes from the "slide step" and shortening up the delivery time to the plate. Many of the hardest throwers in the MLB throw exclusively without a windup.
My son converted to stretch only pitching his Sr year in college and threw harder than he ever had from the windup.