Mejia experienced stiffness and pain in his right elbow and was unable to enter Monday's 3-1 win against the Washington Nationals. He was dispatched to New York on Tuesday.
MRI, X-rays and an examination by team doctor David Altchek at the Hospital for Special Surgery in Manhattan revealed inflammation in the back of his pitching elbow. Mejia received a cortisone injection.
The Mets placed Mejia on the disabled list, backdated to Sunday. Right-handed reliever Erik Goeddel has been promoted, after failing to make the team out of camp.
Manager Terry Collins indicated Monday that if Mejia missed time, Jeurys Familia would ascend to the closer's role, with Carlos Torres likely serving as the primary setup man. Prospect Rafael Montero, whom the Mets hoped to ease into relief work, now may handle the seventh inning. Montero worked as a starting pitcher in the minors.
The Mets have two accomplished late-inning relievers in the final stages of rehab work in Port St. Lucie, Florida, but neither will be rushed back, general manager Sandy Alderson said.
Vic Black opened the season on the disabled list with shoulder weakness. He has yet to pitch in games on back-to-back days against minor leaguers. That is a prerequisite to being activated from the DL, according to Collins.
Bobby Parnell, who preceded Mejia as closer, underwent Tommy John surgery last April 8. The Mets intend to wait until later this month to bring Parnell back to the majors.