Any player, not listed on the final rosters (see post=Final revised rosters) for the 12 teams may be put on your card.
Provided that he played 400AB/100IP for starter/50IP for a reliever in ONE season for your assigned club.
So, for example, you could draft Tommy John- since he is not listed on the final rosters and meets the requirements for the White Sox (the Mod Yankees, and Dodgers could also try and draft him.
Once the draft is over, the Pre War Yanks can try and claim him as well, and after game 120 the Indians could try and claim him).
Once the draft has run, ANY player (who meets the club requirements; 400/100/50) can be claimed in FA, including those listed in the "Final revised Rosters" who were not drafted.
So, if tyou played it cute and didn't draft Joe Jackson, the Indians could claim him.
NOTE: some players have played 400/100/50 for a career for a club, but didn't do it in a season; make sure they meet the single season requirement.