For many baseball fans, this is the most exciting week (prior to September) of the season.

Who's on the move? Will teams get the arm or bat they covet? What long-established players or stars will find themselves in a new city and uniform very soon now?

It's that time of year when websites like mlbtraderumors.com see intense traffic, when twitter feeds and Facebook pages of players and teams are checked every few minutes, when fan chat-rooms fill up with speculation, hope, and yes, despair.

At midnight next Sunday, July 31, the "Trade Deadline" arrives. It doesn't mean there's an end to trading, as August 31st presents yet another deadline; we'll talk about the mechanisms of waivers that will be at work on Monday, August 1, later in this article.

This year some teams that have been habitual sellers have taken on the role of potential buyers, as with the Cleveland Indians, who, after their hot start and then cooling off, are in the thick of the AL Central division race. Just a few years ago the Indians dismayed their fans by dealing away star players such as C.C. Sabathia, Cliff Lee, and Victor Martinez. This year, the Indians (like others) are seeking an outfield bat to fill the void left by the injuries to Shin Soo Choo and recently Grady Sizemore. The Indians, thanks to the trades of those past seasons, have a well-stocked farm system and chips to deal with. They are one of the most interesting stories in this season.

The July 31 deadline is important because on August 1st teams will no longer be able to trade in unencumbered fashion. They will have to put a player through the process known as waivers. This means a player must be made available to other teams, who can put in a claim. In reality, there are many August deals that happen, and some that don’t when a savvy General Manager can intervene to keep a rival, say, from acquiring a key player.

In revocable waivers a team takes a player off its 40-man roster and puts him on the waiver wire. This is a surreptitious process unknown to the player and (usually) the outside world in general. On the 30 Front Offices (FO’s) are aware of who is on waivers.

Sometimes teams do this with a player they want to trade; sometimes they do it with a player they might trade if there is interest. Let’s say the New York Mets put Carlos Beltran on waivers (assuming they don't trade him beforehand); first the teams in the NL in reverse order have their chance to claim him (this would start with the Houston Astros, ending with the Philadelphia Phillies). If no NL team claims Carlos, then the AL teams in reverse order get their chance, starting with the Seattle Mariners and ending with the Boston Red Sox. Teams have two business days from the time a player is waived to put in a claim. If no one claims Carlos, he has cleared waivers and can be traded. If another team claims him then the Mets would have the following options:

1)The Mets and the claiming team (say the Cardinals) can work out a trade. Any player from the Cardinals’ 40-man roster would then also need to clear waivers.
2)The Mets can tell the Cardinals, “He’s all yours” and the Cardinals now assume Carlos’ salary and contract.
3)The Mets can pull Carlos back, in effect saying, “We’re not serious”; they cannot repeat the process with that player again for 30 days.

Now we have what are called irrevocable waivers. This works a little differently. This means a club cannot “pull back” a player and cannot use him as so-called trade bait during the process. This is usually used when a team wants move a player off its 40-man roster for the purpose of giving him his release (in fact any player being released must go through irrevocable waivers).

Not always, though. The Boston Red Sox famously put Manny Ramirez on irrevocable waivers several times starting in 2003; any prospective claimant would have had to pay a $25,000 waiver fee, and then be fully responsible for Manny’s contract. No one ever claimed Manny, and neither did the Red Sox release him before finally trading him to the Los Angeles Dodgers on July 31, 2008.