Destructoid has posted their NBA 2K12 hands-on preview. It looks like you can use any player in the NBA and use him in the Create a Legend mode.
Having the option to jump to the next key game really opens the door for My Player to be NBA 2K12's mode of choice. It takes all the great action of the regular game and boils it down into a condensed 10-to-15 game personal experience. And if creating a rookie from scratch isn't for you, there's always the Create A Legend mode that does practically the same thing with any player in the game.