Wondering why MLB players can be traded after the trade deadline? Here is a simple explanation
The first thing you should know is that what is generally referred to as the MLB's "trade deadline" is really called the non-waiver trade deadline. This deadline is on July 31 every year. Prior to the non-waiver trade deadline, any team can negotiate a trade with any suitor, but after July 31, a new process is put into place.
If you would like to trade a player after July 31, you must begin by placing that player on Major League waivers. Suitors will then have 48 hours to put a claim on that player. At the conclusion of the 48-hour period, one team is awarded a waiver claim on the player. As far as how it is decided which of the claiming teams is awarded the waiver claim, it works similarly to a draft.
The team with the worst record gets the first opportunity to claim the player, then the team with the second worst record, and so on. The twist is that the teams in the same league as the player's current team get waiver priority over the teams in the other league. For example, the Minnesota Twins - an American League team - just placed Justin Morneau on waivers. All of the American League teams will get a chance to claim Morneau before any National League teams get a chance. Waiver priority in Morneau's case will go to the AL teams in order of worst-to-best record, and if no AL team claims him, priority will go to NL teams in order of worst-to-best record.
Once a team is awarded a waiver claim on a player, the player's current team and claiming team will have 48 hours to hammer out a deal. The current team then has three options: agree to the terms of a trade with the claiming team, reject the waiver claim and bring the player back to their Major League roster, or give the player to the claiming team for free.
There is always the possibility of a player making it through waivers unclaimed. If this happens, the player's current team is allowed to negotiate freely with any team they want.
There is an August 31 trade deadline for waiver trades - any player acquired via trade before that date may play in the postseason. Players can be acquired via trade after August 31, but they may not participate in the postseason.
I think that covers just about everything to do with the post-trade deadline waiver process, and I hope that you now have a good understanding of how this somewhat confusing process works.