What is the September roster expansion?

Starting September 1st, players on the reserve can be activated and brought into the dugouts. However, since the pandemic, the number of players has dropped significantly. What are the rules of the call ups and how do they benefit teams?    Get 20% off your first Slab Pack or card purchase by going to ArenaClub.com/FOUL and use code FOULSee omnystudio.com/listener for privacy information.