Although they have not thrown an MLB pitch in 2023, Greg Holland threw 9,662 pitches that were tracked by the PITCHf/x system between 2010 and 2022, including pitches thrown in the MLB Regular Season, the MLB Postseason and Spring Training. In 2022, they relied primarily on their Slider (88mph) and Fourseam Fastball (94mph), also mixing in a Curve (78mph).
In 2022, compared to other RHP:
His slider is much harder than usual. His fourseam fastball has much less armside movement than typical, has essentially average velo and results in somewhat more groundballs compared to other pitchers' fourseamers. His curve (take this with a grain of salt because he's only thrown 6 of them in 2022) is basically never swung at and missed compared to other pitchers' curves, has primarily 12-6 movement and results in more flyballs compared to other pitchers' curves.