This afternoon, I was trying to think of the greatest “superstar” player who was traded away from the Yankees while he was still in his prime. To the best of my research/knowledge, it has to be Rickey Henderson.
For those who don’t know, on June 21, 1989, the Yankees traded Henderson to the Oakland Athletics for Greg Cadaret, Eric Plunk, and Luis Polonia.
Number two on this list would probably be Bobby Bonds.
On December 11, 1975, the Yankees traded Bonds to the California Angels for Mickey Rivers and Ed Figueroa.
In terms of impact on the team, the Bonds deal was great and the Henderson deal was not a winner.
These are the only two times that the Yankees ever traded away (what was then) a current offensive superstar.
Before looking, I would have thought that it happened more often.