As of 6 p.m. ET Tuesday, playoff roster possibilities are essentially set. That hour brings an end to the trade deadline and the movement of players on 40-man rosters. Until 2019, players could be traded after the deadline if they passed through waivers. The advent of the single trade deadline has made it almost mandatory for contending teams to upgrade their roster now. It is the closing of an acquisition window you ignore at your own peril.
That is why we have seen a flurry of activity in the past few days. And why more is still to come. Here are the biggest story lines still in play as the clock runs out on preparing for October.
