"The best part is he's done it before," manager Terry Collins said of Mejia's history in the bullpen. "So he should be able to adapt to it pretty fast."
Mejia made his final start for Buffalo on Saturday, giving up five unearned runs over 4 2/3 innings. He has posted a 2.57 ERA in seven rehab starts split between three Minor League levels, working his way back from last May's Tommy John surgery.
Once Mejia begins pitching in relief, the Mets will give him two weeks to adjust to the role. If all goes well, he could join the big league bullpen before the end of June -- though he first needs to prove that he can pitch effectively on back-to-back days.
"If he gets here, and when he gets here, we'll make our own assessment of what needs to be done to make sure he stays OK," Collins said.
Mejia, 22, made his Major League debut as a 20-year-old in 2010, posting a 4.62 ERA in 30 relief appearances and three starts.