Josh Byrnes| 37, Arizona Diamondbacks
Under Byrnes, who played first base at Division III Haverford, the Diamondbacks rebuilt in 2006 and made the playoffs in 2007.
Theo Epstein | 34, Boston Red Sox
Until Daniels, Epstein was MLB's youngest-ever GM. He's also the new generation's ace. In his six-year tenure, Boston has won two World Series.
Andrew Friedman | 31, Tampa Bay Rays
The ex — Bear Stearns analyst and third-year GM is getting good returns on his investments in young players. Tampa Bay is having its best-ever year.
Neal Huntington | 39, Pittsburgh Pirates
"I'm here to change things," Huntington says. In year one, he has hired a manager, replaced most of the front office, and upgraded farm-team facilities.