13. Ryne Sandberg
Sometimes a team will look back on a trade and realize they made a huge, huge mistake. Teams in all sports, all throughout history have been on both sides of this. The Chicago Cubs made a bad deal in 1964 trading Lou Brock to the St Louis Cardinals. Two decades later, they made a really good one with the Philadelphia Phillies acquiring Larry Bowa and Ryne Sandberg before the 1982 season for Ivan de jesus.
It took a couple of years, but in 1984-1993, Sandberg was an NL All-Star. Sandberg led the league in runs three times, triples once and homers once with 40. After winning his first of nine straight gold gloves in 1983, 1984 was a season to remember for Sandberg.
He would take home the NL MVP, hitting .314 with an .887 OPS, 19 homers, 84 RBI and a the league leading 19 triples.
Sandberg started to decline and in 1994, before the strike, he would retire. However, like Michael Jordan once did in Chicago, he would come back for the 1996 and 1997 seasons.
All told, Sandberg is fifth in homers among second baseman, and would be elected into the Hall of Fame in 2005.