The Padres optioned Weathers to Triple-A El Paso prior to Wednesday's game against the Rockies.
San Diego recently moved from a six-man to a five-man rotation, resulting in Weathers shifting to a bullpen role. Because the Padres are still keen on developing Weathers as a starter long term, he'll head to Triple-A for the time being so as to remain on a normal throwing schedule. Weathers is presumably the first pitcher in line to join the big-league rotation if one of the Padres' five starters should miss time at any point.