Jordan Zimmermann lost for the first time since June 17 after the Marlins scored three times in six innings on Tuesday.
Nationals designated C Dan Butler for assignment.
Nationals acquired RHP Jonathan Papelbon and cash considerations from the Phillies in exchange for RHP Nick Pivetta.
According to FOX Sports' Jon Morosi, a trade sending Jonathan Papelbon to the Nationals has been "agreed upon."
Jim Bowden of ESPN reports that the Nationals are "at the finish line" on a trade for Jonathan Papelbon.
Nationals optioned OF Matt den Dekker to Triple-A Syracuse.
Nationals sent INF Emmanuel Burris outright to Triple-A Syracuse.
Nationals activated 1B Ryan Zimmerman from the 15-day disabled list.
Nationals activated OF Jayson Werth from the 60-day disabled list.
According to Barry Svrluga of the Washington Post, the Nationals are nearing a deal for Jonathan Papelbon.
Todd Zolecki of MLB.com hears that Jonathan Papelbon or his agents are talking to the Nationals about a potential trade.
Jim Salisbury of CSNPhilly.com hears from a baseball source with knowledge of the situation that Jonathan Papelbon "will be traded" by Friday's deadline.
FOX Sports' Ken Rosenthal reports that the Nationals are "making progress" on acquiring Jonathan Papelbon from the Phillies.
Ryan Zimmerman (foot) will be activated from the disabled list for Tuesday's game against the Marlins.
Jayson Werth (wrist) is set to be activated from the disabled list Tuesday.