MLB 09 The Show - Franchise Mode Enhancements

When we set out this year’s plan, one of our goals was to blow out the personnel aspects of the Franchise experience. Starting with the beginning of spring training, the rosters you will carry into spring will be those of their real-life counterpart, the long awaited 40-man rosters. Now you will have to manage your Spring Training roster a little more carefully to ensure your young players get the looks they need.
Moving on to the regular season, you will now be dealing with many of the various roster-related items all GMs have to deal with. You will be in control of designating players for assignment, waiver transactions, handling Minor League options, and managing your 40-man roster. Once in June, you will have the Amateur Draft to participate in. Along with drafting players, the Amateur Draft also includes Supplemental picks for those teams that failed to re-sign Type A or Type B free agents in the offseason.

Once your season hits September, your 25-man roster will expand to the full 40-man where you will then have to decide who get’s the call and who doesn’t. If your Franchise is successful enough to make the playoffs, you will have to manage your rosters accordingly, and will only be able to replace players on the roster between series.
Via PS Blog