Simpson will start a bullpen game Wednesday against the Phillies, Mark Zuckerman of NatsJournal.com reports.
Washington will lean on its bullpen to get through Wednesday's series finale in an effort to buy some extra rest for Cade Cavalli, who has already pitched 164.2 innings this year. Simpson will take the mound to begin the game despite coughing up three runs without recording an out in his last appearance, and he'll likely remain in the game for a few frames before turning things over to another reliever.