3:26pm: The two teams have agreed to the trade, pending physicals, Ken Rosenthal tweets.
3:25pm: The Bucs are close to a deal to receive Niese for Walker, Buster Olney tweets.
3:19pm: The Pirates and Mets are close to a trade involving Neil Walker, the New York Daily News' Kristie Ackert tweets. There's little to do but wait and see what happens; Jon Niese's name has already come up in connection with a potential Walker deal, and that makes sense to a degree, since the Pirates do need starting pitching. A one-for-one deal wouldn't work, however, since Walker is the better player. The Bucs would likely need to get someone else too, or at least one would hope. Niese, a veteran lefty, saw his strikeout rate drop to 5.8 batters per nine last year. He's a ground ball pitcher. Essentially, he bears some similarities to Jeff Locke, although he's more expensive (and has a better track record).
In any case, it seems increasingly likely that the Pirates will in fact deal Walker, perhaps in the next hour. The Angels, Nationals and Orioles had all previously been connected to Walker.