On this day in 1973, the Cubs traded their Hall of Fame third baseman Ron Santo to the Chicago White Sox. Santo was a nine time all-star (including 1973), but was clearly on the downside of his career.
In return for Santo the Cubs got pitcher Steve Stone, catcher Steve Swisher, and pitcher Ken Frailing.
It actually turned out to be a good deal for the Cubs. Santo only played one year for the White Sox and retired after hitting a woeful .221 for them. Steve Stone, on the other hand pitched three years for the Cubs (including a 12-win season in 1975), as did Ken Frailing, and Steve Swisher became a National League all-star in 1976.
Santo was very upset by the trade, but he obviously eventually forgave the Cubs. His #10 flag will fly on the Wrigley Field foul pole forever.