Mitch Haniger.
That’s the only player in the Mariners organization projected by the Steamer projection system to be an above-average hitter in 2021. Steamer, for those unfamiliar, is one of the major public MLB projection systems along with, among others, Marcel, PECOTA, and ZiPS. As with all projection systems, the numbers you see are a mean/median of a multitude of projected outcomes, with the final “answer” being something based around past production, aging curves, pitch tracking, and run environment. It’s less reliable with younger players, particularly without much minor league data to go off, which will only be exacerbated after 2020’s canceled MiLB season.