Currency. Just like Cecchini. He undoubtedly can play SS for SOMEBODY, and perhaps even well (the glove is clearly good - not Iglesias good, but good). Brandon Crawford makes a nice living. I think this is the sort of evaluation you are making internally all the time as a franchise. Which prospects are our future guys and which ones are trade pieces. Obviously the venn diagrams intersect some but for teams like the Sox and Yankees who yes "should" be putting together a contender every year - sitting on the prospect haul a la some college football team flat doesn't make sense.
Right now to me Bogaerts, Betts, Swihart represent future core - there is no such thing as untouchable, but you definitely need premium, controllable big league value coming back.
Owens, Rodriguez, Margot are a half step down. The former two because they are pitchers (and there is always a wee bit extra risk with pitchers generally) and the latter because he is not at AA yet. (remarkable ceiling but still quite a bit of variance in his ultimate fate)
Then you start getting into your Cecchini, Bradley, Merrero, the rest of the Ranaudo, Webster, De La Rosa, Barnes level. There are starters here, but probably not elite ones - and the industry is in relatively sharp disagreement over what the best of this crop actually is. You are dealing either with high upside/low probability (De La Rosa, Bradley at this point) or low to modest upside with high probability (Vasquez, Merrero). This is where the trade stuff comes from ideally - because other teams have favorites from this list.
Then I think you also have the guys like Devers, Chavis, Ball, Sam Travis. High ceiling again, but low probability just by virtue of how far away they are from the show right now. These are the ones I agonize about because I like them and if you trade to fill a current need, they are ones likely to make developmental leaps which put egg on your face.