If this is the new MLB then I’m out

The September callups benefit the others on your 40 man roster. The minors, excepting the few playoff teams, have their season end on September 1st. That gives minor league players an extra month off. Giving the players a month to acclimate themselves to the majors helps a lot also. But Mattingly is right September baseball is a different game because of the bloated rosters.  The solution is simple. Carry a 40 man roster but name a 25 man roster for each game. That gives a few more options (last night's starting pitcher, tomorrows starting pitcher won't be on the game's roster, obviously), but end the 15 pitching change games.