His composition of fastball%, breaking ball%, changeup% is not statistically different than Santana's. Duffey also has a pretty significant reverse platoon split over his career: 3.14 xFIP vs LHH and 4.53 vs RHH (3.25 and 4.61 in 2016, respectively), nearly doubles his K/BB ratio vs LHH and RHH have nearly a 100 point increase in wOBA vs lefties. Most successful mid-rotation major league starting pitchers generally have 2 above average to plus pitches and average to above average command. Third and fourth pitches are generally only "show me" type pitches to keep hitters honest and are rarely even major league average in quality. We needn't look any further than the other Santana that pitched for the Twins to see this. In 2007, the only year that pitch f/x is available on fangraphs and Johan's last year with us, he threw a 4-seamer 63.9% of the time, his famed change-up 26% and his slider only 10.1% of the time. If the average PA lasts only 4-5 pitches then he is throwing his third pitch, the slider, at most once every other PA. And Johan was the definition of an ace type pitcher, not merely a mid-rotation type.