The Pittsburgh Pirates, who are leading the NL Central with a 9-6 record, open a four-game series with the Washington Nationals (7-8). The Pirates took two of three games from the Chicago Cubs over the weekend.

Hunter Barco needs to start. The Pirates’ busy bullpen, meanwhile, could use an extra arm. That was manager Don Kelly’s explanation for Monday’s roster move, Pittsburgh optioning Barco to Triple-A Indianapolis and recalling Evan Sisk,