Zuck, in this morning's chat, says the Nats are going to need a defensive OF on the bench, and it will likely be one of Stevenson, Bautista, or Robles. He also suspects they may keep Severino as a PR for Weiters late in games.
So assuming Harper and Werth are able to play, that would set the bench as: Lind, Kendrick, Difo, Lobaton, speedy OF and Severino.
