Ellis' playing time will take a hit following the promotion of catching prospect Francisco Mejia.
Ellis went 3-for-3 with a walk and an RBI in Saturday's 5-3 loss to San Francisco.
Ellis went 2-for-4 with his first home run of the 2018 season in Saturday's win over the Dodgers.
Ellis started and went 0-for-2 with a pair of walks and a run scored in Wednesday's loss to the Giants.
Ellis started behind the dish and went 2-for-4 in Sunday's 14-2 loss to the Mets.
Ellis signed a minor-league contract with the Padres on Wednesday, AJ Cassavell of MLB.com reports.
Ellis will start at catcher and bat second Sunday against the Reds, Andre Fernandez of the Miami Herald reports.
Ellis got the start behind the plate Sunday and went 2-for-4 with a double, a solo home run and a second run scored.
Ellis has only 13 hits and two RBI in 65 at-bats this season.
Ellis is batting .213 this with no extra-base hits and two RBI in 55 at-bats this season as the backup catcher in Miami.