Neal Huntington says the Pirates could trade from their relief depth:
Huntington on bullpen depth: "Maybe it’s a chance to move a guy that can go help someone else to add a piece."
I think it's fair to assume that Jason Grilli, Mark Melancon, Tony Watson and Justin Wilson all have close to 100 percent chances of winning roster spots, which means that the Pirates won't have enough spots for all their relievers -- Vin Mazzaro, Jeanmar Gomez, Bryan Morris, Stolmy Pimentel and Andy Oliver are all out of options. Neal Huntington has already said that Pimentel is pretty much assured of a job, and Oliver almost certainly isn't getting one, sot hat leaves Mazzaro, Gomez and Morris for two spots.
Travis Sawchik thinks Morris will likely have a clear shot at a job, and it makes sense to me that the Pirates would think that. Morris was dreadful last year, but Clint Hurdle frequently used him in the late innings anyway, so the Bucs seem to like him. He clearly has more upside than Gomez, at least. That means Mazzaro and Gomez are the most obvious trade candidates. But maybe there's a way for the Pirates to ship off Watson or Wilson -- both fairly valuable properties -- to get a first baseman.