Prior to being traded to the Red Sox, Joe Cronin was the on-field leader of the Washington Senators, and he was the runner-up for the MVP in 1933.  Cronin was dealt to Boston, and the Sox coveted him not just for his bat, but for his mind, as he became their Player/Manager.

Dutch Leonard was a huge cog in the machine that made the Red Sox a powerhouse team in the 1910s, and while he has not received the due that he deserved, there is a good chance that they don't win the 1915 and 1916 World Series.  

A Second Round pick in 2002, Jon Lester debuted for the Red Sox in 2006, and in the next season, he was a small part of Boston's 2007 World Series win over Colorado.  He won a game in the Fall Classic, which would be the springboard for what would transpire next.