The Padres optioned Sullivan to Triple-A El Paso on Friday.
Sullivan is the odd man out for San Diego following the return of Xander Bogaerts (shoulder), who was reinstated from the IL on Friday. Sullivan was rarely able to see the field while behind Luis Campusano and Kyle Higashioka on the depth chart at catcher, appearing in just four games since being recalled from the minors June 22. He'll return to being organizational depth at Triple-A.