Major League Baseball's July 31st trade deadline has passed, but plenty of major league players will still be traded before the season is over. July 31 is commonly referred to in Major League Baseball as "the trade deadline," but the more accurate term is "non-waiver trade deadline." Teams may still make trades during the months of August and September, but the rules are very different.
Starting August 1 of each season, clubs can put players on "special waivers," also known as "major league waivers," "trade waivers," or "revocable waivers." Any player who could possibly be traded can be put on waivers and if they are claimed, the club can call them back without losing the player.
If a player is not claimed within the 48-hour waiver period, he can be traded to any MLB team during the month of August. If multiple teams put in claims on the same player, only one club can have the priority waiver claim. Priority is given to the team with the lowest winning percentage in the same league, from worst to first, and then from worst to first in the other league.
Clubs generally do not put in a waiver claim unless they are genuinely interested in a player or, in a few cases, they want to block a rival team from being able to acquire the player. However, the club that puts in a claim should be prepared to take on the full contract of the player, because that player’s current club can just let the player go if they don't recall him off waivers. A club that is not a contender has no reason to block another club from acquiring a player, but they might want to put in a claim on a player who is under contract in future seasons.
The list of players who are placed on waivers every August is quite impressive. Since there is no risk to putting a player on revocable waivers, clubs will often put many players on waivers, hoping that the player(s) they might trade will get through with the pack. The majority of players clear waivers. Clubs don’t want to put in claims, disrupting the plans of another club, for fear of retaliation either that season or in another season when they would like to get a player through. The protocol basically goes, "You let this guy through for me and I’ll let that guy through for you."
Major League Baseball does not publish the list of players who are placed on waivers, so we won't even know which players are eligible to be traded. Each season, information leaks out and sometimes that information is intentionally leaked for one reason or another. All clubs have access to the full list of players who are placed on special waivers.
The most likely players to be traded after the trade deadline are those that non-contending clubs would like to avoid paying, but good enough to help a contending team in their playoff run. Those players are sometimes claimed off waivers and just let go, and other times clear waivers and are traded.
Good players on National League teams are less likely to make it through waivers to the Tigers, because they need to clear all NL teams first. The Tigers have a better shot at players in the American League, where they are currently seventh from the bottom of the standings. Unlike the Rule 5 draft, waiver claims can not be traded. Teams at the top of the pecking order cannot have teams lower down the list put in a claim for them. The player can’t then be moved to another team without going through waivers again.
Some players that the Tigers have acquired during August in recent years include Aubrey Huff, Neifi Perez, Freddy Garcia, Delmon Young, and Jeff Baker. Players who are not on a team's 40-man roster do not have to clear waivers to be traded. It seems that the Tigers are more likely to trade players away this year than they are to acquire any major league players.
One restriction is that a player can only be recalled once during the month. If a team puts a player on waivers, and a claim is made and they recall the player, the next time that they put the player on waivers, the move is non-revocable.
After August 31, all waivers expire, a new waiver period begins, and the process starts all over again. A player must again clear waivers before they can be traded. However, players who are traded in September are not eligible for postseason play.