Sullivan will start at catcher and bat ninth in Wednesday's game against the Nationals.
The Rockies are giving All-Star Hunter Goodman a day off from catching but keeping his bat in the lineup at designated hitter, so Sullivan will get a turn behind the dish in the series finale. Sullivan has started in just two of the Rockies' last six contests, and his playing time will likely remain scarce so long as Goodman is healthy and the team continues to carry three catchers (Sullivan, Goodman and Braxton Fulford) on the roster.