If you could get a guy to throw only 90-92 mph and save that 96+ for maybe every 5-6 pitch, it would keep hitters off-balance more. I also think more pitcher need to learn better pitch combinations. By this, I mean, pitches that look simpilar but have slightly different movement. 4-seem to 2-seem, 4-seem to slider, slider to cutter etc... Mastering changing speed with every pitch gives you countless combinations, that if you can control well, make it near impossible to hit.