Emilio Bonifacio exited Tuesday's game against the Red Sox with a left rib injury.
Bonifacio was nailed with a ground ball. He'll be re-evaluated Wednesday.
Nationals designated C Dan Butler for assignment.
The move clears a spot on the 40-man roster for Jonathan Papelbon. Butler, 28, has hit .231/.315/.312 with one homer at Triple-A this season and has a good chance to clear waivers.
Aaron Brooks will be recalled to start on Saturday against the Indians.
Acquired from the Royals in the Ben Zobrist deal, Brooks holds a 3.71 ERA over 18 appearances -- 17 starts -- at Triple-A this season. The A's will keep Drew Pomeranz in the bullpen.
Devon Travis left Tuesday's game versus the Phillies after aggravating his left shoulder injury.
Travis returned to action last month after missing five weeks with a shoulder malady. It's unclear how he aggravated it, but the young second baseman might have to go back to the disabled list.
Phillies acquired RHP Nick Pivetta from the Nationals in exchange for RHP Jonathan Papelbon and cash considerations.
Ranked prior to the season by Baseball America as the Nats' No. 10 prospect, Pivetta holds a 3.02 ERA with 78 strikeouts over 101 1/3 innings between High- and Double-A this season. He could be a mid-rotation starter if things work out.
Nationals acquired RHP Jonathan Papelbon and cash considerations from the Phillies in exchange for RHP Nick Pivetta.
He'll slide into the closer role for the Nats, pushing Drew Storen to the eighth inning. Papelbon also agreed to drop his 2016 salary from $13 million to $11 million in order to have the vesting option exercised, so he's under contract through next season. Ken Giles will take over as the Phillies' closer.
The A's will use Edward Mujica as their closer following the trade of Tyler Clippard.
He hasn't been the club's most effective reliever, but how he's been used indicated that he'd probably be the guy. Having closer experience surely helped him, too. Mujica has put up a 3.68 ERA and 12/2 K/BB ratio over 14 2/3 innings since joining the A's in May. Scoop him up in your league if he's still available.
Mark Saxon of ESPNLosAngeles.com reports that the Dodgers have yet to ask Alex Guerrero about waiving the opt-out clause in his contract in exchange for money.
Guerrero has a clause in his contract that says he can become a free agent at the end of the season if he's traded. It was reported recently that he might be willing to waive it in exchange for some cash, but apparently the Dodgers have yet to ask him if that could happen. It doesn't mean it won't, of course, as there are still a few days before the deadline.