Even offseason deals involving legitimate can't miss prospects often don't turn out all that well for the team receiving the prospects.And for each of these deals, there was some contingent of fans who were deeply upset by the loss of the prospects. Some people consistently overvalue unrealized potential without considering how few of these players actually are truly impactful. To date, the answer is not many and certainly not enough to forego trying to contend.
Kopech and Moncada for Sale. Even with Sale's numerous injuries, Moncada has had only 2 good years out of 7, and Kopech is 14-23 with an ERA+ of 107. Sale has gone 45-27 with an ERA+ of 143 in Boston, and that's with all his injuries reducing his impact.