Melancon will supplant Papelbon as the Nationals' closer a year after Papelbon's arrival bumped Drew Storen out of the role.
Melancon will assume the closer's role, bumping Papelbon from the ninth.
Murphy exited Friday's win because of leg tightness.
Rookie lasts four innings and a depleted bullpen can’t hold down San Francisco in 5-3 loss.
Ryan Zimmerman initiates the first triple play in Nats history to back Max Scherzer’s superb start in 4-1 victory in San Francisco.
Miller has an 11-to-1 strikeout-to-walk ratio, the eighth highest among relievers this past decade.
Lopez is coming off a shutout for Class AAA Syracuse.
Revere will lead off and play center field over Trea Turner.
Revere is hitting a career-worst .213 this season.
The Nationals most big-league-ready catching prospect will join the team Friday.
Papelbon faced just three batters Thursday before he was pulled.
The 23-year-old speedster will again leadoff for Washington ahead of Bryce Harper and Daniel Murphy.
The right-hander got his first career save Wednesday against the Indians.