Ok, I also did some research on this as well. Here's what I found:
Keith Foulke has lost his closer's job, manager Jerry Manuel announced. Antonio Osuna and Damaso Marte will begin to get save chances.
Manuel said the switch is only temporary. On one hand, it's ridiculous that Foulke is losing his job. He's blown just two saves all year. On the other hand, this is an effort by Manuel to get Foulke more work, which should be a very good thing. Foulke has two saves in three chances since April 26, and he was not pitching enough to stay sharp. A few two- or three-inning outings should benefit him. We'd be surprised if Osuna and Marte combined for more than three or four saves before Foulke gets his job back. They're worth picking up in AL-only leagues, but don't expect much. Foulke still has value in all leagues.