Dickey is scheduled to be called up from Triple-A Buffalo after the Mets finish a two-game series at Atlanta. He'll start the opener of another brief series at Washington. The knuckleballer has previously pitched in the big leagues with Minnesota, Seattle and Texas.
The Mets demoted Oliver Perez to the bullpen. New York still hopes to convince Perez to go to the minors, a team source told ESPNNewYork.com's Adam Rubin. The lefty is 0-3 with a 5.94 ERA in seven starts this season.
The Mets also are expected to put left-hander Jonathon Niese on the disabled list with a mild strain to his right hamstring.
The other vacancy in the rotation comes up Friday against the Yankees. It'll go to Takahashi, who is 3-1 with a 3.12 ERA in 15 games out of the bullpen.
Information from The Associated Press contributed to this report.