Although he has not thrown an MLB pitch in 2018, Jake Arrieta threw 19,615 pitches that were tracked by the PITCHf/x system between 2008 and 2017, including pitches thrown in the MLB Regular Season, the MLB Postseason and Spring Training. In 2017, he relied primarily on his Sinker (92mph), also mixing in a Curve (79mph), Slider (88mph) and Change (88mph). He also rarely threw a Fourseam Fastball (93mph).
Basic description of 2017 pitches compared to other RHP:
His sinker is a prototypical pitch with few remarkable qualities. His curve generates more whiffs/swing compared to other pitchers' curves and has slight glove-side movement. His slider is thrown extremely hard, results in more flyballs compared to other pitchers' sliders and has less than expected depth. His change is much firmer than usual, has slight armside fade and has some natural sink to it. His fourseam fastball has essentially average velo and results in somewhat more groundballs compared to other pitchers' fourseamers.