It means that we are in the weird through-the-looking glass trade deadline portion of the season where all sorts of shenanigans tend to ensue.
Up until July 31, teams can trade with each other freely. This is when you see player-for-prospect swaps like the Kosuke Fukudome trade, or the Carlos Beltran for Zach Wheeler exchange. But teams can actually continue trading players through the end of the season, as long as the players pass through waivers.
The waivers system allows a team to make any player available for the rest of the teams to claim. Teams are given the option to make a claim in reverse order of their place in the standings. Once a player is claimed, he can be pulled back by the original team (which is what happens in most cases) or the teams can agree to make a trade, or the original team can simply let the player go.
While this process can go on up until the last day of the season, the it tends to go into overdrive at this point in the summer because Aug. 31 is the last day a player can be moved and still be eligible for postseason rosters.
As examples from this year, first baseman Carlos Pena was claimed by the Yankees, but ESPN reported that a deal with the Cubs was unlikely.
Pitcher Aaron Laffey was also claimed by the Yankees and the Mariners, happy to be free of his contract and roster spot, let him go without asking for anything back in a trade. Apparently, so were the Yankees, who dropped him the next day.
Nearly all players are put through waivers. Even superstars like David Wright of the Mets are put up on waivers (reportedly claimed by the Rockies), though that doesn’t mean he is going to be traded or let go. It is unlikely the Mets would part with a young, reasonably-priced infielder who has become the face of their franchise, even in a down year.
The process is just another way for teams to indicate interest, engage in subterfuge, or just simply keep their baseball operations folks busy. For instance, the Giants put a claim on relief pitcher Heath Bell of the Padres and there is mixed speculation on whether it was done to try and secure his services, block him from going to the division leading Diamondbacks, or both.
As a reasonably-priced player who is likely to bring back draft compensation as a Type-A free agent this offseason, Bell is a low-risk waiver claim target either way. But teams are smart to beware being stung by the process.
The MLB Web site explains how this blocking method can blow up in a team’s face. In 1998, Toronto let closer Randy Myers go to the Padres after the put a claim in just to block a trade to the Braves. As MLB bluntly concludes, “Myers appeared in just 14 1/3 innings for the Padres, going 1-3 with no saves, and he did not pitch after the ‘98 season, leaving San Diego on the hook for the balance of his $13.6 million salary for 1999-2000.”