What happened: The September roster expansion adds two active-roster spots per club, up from 26. Teams can use the added places for pitchers, position players and returning players.

Why it matters: The extra flexibility arrives during the season’s final three weeks, when contenders can manage workloads and injuries more closely. Roster decisions can also create late opportunities for players moving up from the minors.

What to watch: Watch for clubs to announce individual promotions and corresponding roster moves.