The Mets recalled 20-year-old Ruben Tejada from Triple-A Buffalo to fill Castillo's starting spot. Omir Santos was called up from Double-A Binghamton, giving the club three catchers on the big league roster.
The moves were made Friday before the opener of a three-game series against Florida.
Castillo was put on the 15-day DL, retroactive to Wednesday, with a bruised right heel. He had a CT scan Thursday that was negative, the team said.
Castillo has been hobbling for weeks, first because of pain in his left foot, then his right. He is batting .241 with no homers and 14 RBI.