Carlos Silva » PitchFx » Overview | FanGraphs Baseball
Assuming the Pitch F/DX data is correct, Carlos Silva has stopped throwing a four-seam fastball and switched to a two-seamer. Additionally, it has imporved his change-up's effectiveness as that pitch is being thrown twice as often as it was last season.
There is no change in velocity between the two-and four-seamer and no change in velocity differential between the two-seamer and the chnage up.
Of course, it could just be a lucky BABIP as his May 1st start looked more Silva-esque.