Start with Ellsbury pathetic performance this month which has YET to score a run. He sees two+ pitches average his first 3PA each night, promptly retired on a weak hit ball to second. Nava meanwhile has score as many runs on the season as Ellsbury with 50 less AB, while doesn't have Pedroia, Ortiz and Napoli behind him most night. Ellsbury is making it easy to let him walk.