Waldron (forearm) made his first rehab appearance with Triple-A El Paso on Sunday, tossing 2.1 scoreless innings.
Waldron breezed through his 2.1 frames on 27 pitches, yielding just one hit. It was Waldron's first outing in exactly one month, as he's working his way back from a right brachialis muscle injury. If the knuckleballer is added back to the major-league roster at the conclusion of his rehab assignment, he is expected to be used in a relief role.