If you can remember all the way back to mid-2012 you'll remember how painful--but necessary--it was to part ways with Zack Greinke. He was a fan favorite and a very good pitcher. But with free agency--and a large payday--looming and the Brewers will no real chance at the playoffs, Doug Melvin sent Greinke to the Angels for SS Jean Segura, RHP Johnny Hellweg, and RHP Ariel Pena. The former two players are with different organizations now, leaving Pena as the last remaining part of the trade within the Brewers organization.
It's kind of funny because he was pretty universally viewed as the throw-in.