Then there's the new My Player mode, which allows you to create a player from scratch and follow his lifetime career. By completing certain goal-oriented tasks in the Minors, you'll then get called up to the Major leagues -- and once there, you'll find even more career milestones to work towards. Do well enough with your created Joe Schmoe and you'll find yourself unlocking milestones that put him on the track to be the next entrant into the Hall of Fame.
Source - Part one of My Player mode detailed
Source - Part two of My Player mode detailed