Lefty Raul Valdes, whose contract was purchased from Triple-A Buffalo, will take his spot on the 25-man roster and is available for the Mets' afternoon game against the Nationals. In order to clear space for Valdes on the 40-man roster, right-hander Clint Everts was designated for assignment.
With Green on the DL, Mets manager Jerry Manuel said Pedro Feliciano would get most of the opportunities as the setup man, according to The Associated Press.
Green's lone appearance this season came on Wednesday -- when he gave up a run in a one-inning stint against the Marlins -- so his DL stint can be retroactive to Thursday, and the 30-year-old right-hander is eligible to return as early as April 23.
Green made a career-high 79 relief appearances in his first season for the Mets, posting a 4.52 ERA in 2009.
The 32-year-old Valdes, whom Green beat out for the final bullpen spot this spring, posted a 2.08 ERA in six Grapefruit League games. A former Cuban defector, Valdes has never made a big league appearance. He was previously pitching in the Mexican League.
Alden Gonzalez is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.