Without doing any research on it, which I might try to do at some point, I’m guessing there are certain attributes on the Statcast cards that are somewhat predictive and others that are far less so.
Going out on a limb here, I don’t think xBA and xSLG are all that predictive, and hard hit % might not be much more predictive, because they are the result of batted ball which has a high degree of luck attended to it. But I’m guessing K% and BB% are probably more predictive because they reflect more a pitcher’s stuff, the ability to pound the zone and elicit swing and miss. Again, that’s just going out on a limb and making a guess educated by looking at a lot of this stuff, and not taking into account any concerted changes hitters and pitchers make to address weaknesses that could change a guy’s card year over year.