I am not sure that there is an maximum number of players that could be on a varsity baseball team. If so, I would think that the number is larger than 22 players. Lyons Township for instance, has always had very large rosters. I would not think that players who were members on the team during the regular season would not be able to dress for a playoff game.
Phil Fox, the head coach for Downers Grove South, stated that due to the depth of talent and the chemistry displayed during the 2006 summer state finals, he would keep a larger roster this year compared to past seasons. Typical, his teams have consisted of between 20 to 24 players.