Solely to create difficulty for the Red Sox, the Yankees placed a waiver claim on the player going to the Mets in the Billy Wagner trade. By doing so, it forces Boston to keep him on the 40-man roster the rest of the year because (if I understand this correctly) if the Sox had not pulled Carter back, and the Yanks got him, the Wagner trade would've fallen through, so they had to 're-claim' him to ensure the Wagner trade was completed.
The Red Sox and Yankees are suddenly and surprisingly engaged in a game of roster brinksmanship over the fate of Pawtucket outfielder Chris Carter, who is as shocked as anybody to be involved and trying to find a way out of it so he can play in September for the New York Mets.
Carter was one of two players to be named later in the Tuesday deal that sent Mets reliever Billy Wagner to Boston. Because the trade was made after July 31, all players have to clear waivers to play again this season. But the New York Yankees put in a waiver claim to block Carter's move to the Mets, presumably to create roster difficulty for the Red Sox.
Having pulled Carter back from waivers, the Red Sox must now carry him on their 40-man roster for the rest of the season -- a spot they might prefer to use on a pitcher. The trade can't be completed until after the season, denying Carter a chance to play and the Mets a chance to see what they've got in him.
The Sox and Mets are now trying to develop their own strategies to find their way out of the mess, and get Carter to the Mets by Sept. 1.
Take that, Boston!