Although he has not thrown an MLB pitch in 2019, Wei-Yin Chen threw 16,162 pitches that were tracked by the PITCHf/x system between 2012 and 2018, including pitches thrown in the MLB Regular Season and the MLB Postseason. In 2018, he relied primarily on his Fourseam Fastball (92mph) and Slider (85mph), also mixing in a Change (84mph) and Curve (74mph). He also rarely threw a Sinker (91mph).
Basic description of 2018 pitches compared to other LHP:
His fourseam fastball has less armside movement than typical, has essentially average velo and results in somewhat more flyballs compared to other pitchers' fourseamers. His slider generates fewer whiffs/swing compared to other pitchers' sliders, is much harder than usual and has less than expected depth. His change has surprising cut action and results in many more groundballs compared to other pitchers' changeups. His curve has a sharp downward bite, results in somewhat more flyballs compared to other pitchers' curves and has slightly below average velo. His sinker is basically never swung at and missed compared to other pitchers' sinkers, results in more flyballs compared to other pitchers' sinkers and has less armside run than typical.