With Starling Marte going on the DL with a bruised hand last week, the Pirates needed an outfielder. They got one in Marlon Byrd. Byrd, along with catcher John Buck, will head to Pittsburgh along with cash to cover some of their salaries in exchange for 19-year old prospect Dilson Herrera and a player to be named later.
Byrd is having a renaissance year for the Mets. In 117 games, the soon-to-be 36-year old has hit 21 homers, hitting .285/.330/.518 for the season and accruing 3.5 fWAR in the process. I'd assume that Byrd will play right field for the Pirates, who have gotten nothing out of that position all year, but I wouldn't be surprised to see him in left until Marte comes back while Pittsburgh rolls out some combination of Jose Tabata, Felix Pie, and or Andrew Lambo in right.
Buck's inclusion in the trade simply gives the Pirates some depth at the major league level behind the plate. Russell Martin is firmly entrenched as the starter, but the Pirates have gotten nothing from backups Michael McKenry and Tony Sanchez. McKenry's season is done thanks to knee surgery, and the rookie Sanchez is hitting just .220/.267/.341 in 15 games. For the year, Buck is hitting .215/.285/.367, though the 33-year old's statistics have dropped off considerably after a red hot April.
Herrera, the only known prospect heading to New York in the trade, is a good one. He's not one of Pittsburgh's elite guys like Gregory Polanco, Alen Hanson, Jameson Taillon, or Tyler Glasnow, but the 19-year old was a top 15 guy in the organization coming into the season and has hit .265/.330/.421 for the West Virginia Power of the A-ball South Atlantic League while homering 11 times and stealing 11 bases. He's played mainly second base for the Power this year, but has gotten some time at third as well.
It's a solid return for one month each of a pair of players who will be free agents after the season. As for the Pirates, they did what they needed to do without giving up an elite prospect. You can't ask much more than that.