More than 300 ballplayers have spent time with both the Boston Red Sox and the New York Yankees, opposing teams in one of the most intense rivalries in sports. This book examines the century long antagonism between the two clubs, chronicling their storied pasts and their evolution during the 20th century. Several what-ifs are considered: what if Babe Ruth had never been traded from the Red Sox to the Yankees? What if the clubs had swapped Joe DiMaggio for Ted Williams, as was proposed by the owners of both teams? What if Alex Rodriguez had gone to Boston, as was originally intended, rather than to New York? The debate as to which team has made out better with shared players is explored.