Aaron Harang pitched six no-hit innings, using just his off-speed pitches:

Amazingly, Harang hardly used his fastball for six innings, working on his breaking pitches — sliders and changeups, “Throwing them for strikes. I threw some on 3-and-2 counts. I know my fastball always will be there and I’ll need it, always need it, but I worked on keeping the off-speed pitches down in the zone and I kept the hitters off balance.”

Sometimes, the slow stuff can be very effective. Just ask Mike Mussina.