The person spoke to The Associated Press on condition of anonymity because the deal was not yet official. The Pirates will send New York minor league infielder Dilson Herrera and a player to be named later in exchange for two veterans Pittsburgh hopes will help the franchise to its first playoff berth in 21 years.
Byrd is hitting .285 with 21 home runs and 71 RBIs this season and will give the Pirates needed depth in the outfield while leadoff hitter Starling Marte recovers from a wrist injury.
Buck is batting .215 with 15 home runs and 60 RBIs. He is expected to back up Russell Martin.