Chicago general manager Jed Hoyer said on a conference call there are "players to be named (later) on either side," but they "will not affect the balance of the deal."
The Cubs signed Hairston to a two-year deal in the offseason to platoon in right field, but he struggled, batting .172 with eight home runs and 19 RBIs. One of those homers came during Sunday's 4-3, 11-inning win over Pittsburgh. He had 20 last season with the New York Mets.
Now, he's headed to Washington, the latest move in a busy stretch for Chicago.
"Needless to say, he's been a popular name and a guy we've gotten a lot of phone calls on," Hoyer said. "I think he's opened a lot of eyes the way he's thrown the last four, five times out."
The Cubs are also still waiting on third baseman Kris Bryant, the No. 2 pick in the draft, to sign. Hoyer remains confident they'll reach an agreement before the July 12 deadline.
"We're going to make him an exceptionally fair offer," Hoyer said. "If Kris wants to be a Cub and be a professional baseball player, I'm confident that we'll get a deal done. Sometimes, it takes a deadline to make a deal. We have a deadline coming up shortly. In a lot of ways, I think that's a plus at this point."
As for Pineyro, the 21-year-old right-hander has combined to go 6-3 with a 3.24 ERA in 15 starts between Class A Hagerstown and Potomac.
"I think this is a good opportunity for Scott and the Nationals to get more playing time, and I think it was a good opportunity for us to acquire a young pitcher that we liked," Hoyer said.
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