Hughes throws a good portion of his sliders, curveballs, and changeups out of the zone low, but hitters aren't swinging at them. This behavior I believe evidences the weakness of the action on those pitches. Moreover, when hitters do swing at these pitches, particularly when they're in the zone, they rarely miss. By contrast, batters swing at more of Lincecum's sliders, changeups (Splitters), and curveballs, specifically the ones that are low and out of the zone where any contact is likely to be weak. Moreover, they are whiffing much more frequently. This, I believe, evidences the strength of the action on these pitches.