I like the notion of keeping vs. trading.
On the other hand, any team can develop a "surplus" of talent at a given position. When/if that occurs, it makes sense to trade someone.
However, in the case of the Boston Red Sox, they almost never have a surplus of good pitchers. I think the last good pitcher they unloaded was Babe Ruth, and he turned out to be a good bat. Not as great as Verdugo, of course, but good.