(John McDonnell / The Washington Post)

The Nationals made several important changes to the composition of their roster on Tuesday afternoon and now they take the field to face the Mets for the opening game of a three-game series. Jordan Zimmermann (8-3, 2.37 ERA) faces right-hander Jeremy Hefner (1-5, 4.74 ERA). The lineups are here. Talk about the game here.