The Padres optioned Rosario to Triple-A El Paso on Friday.
With Luis Campusano (thumb) returning from the injured list, Rosario will end up as the odd man out on San Diego's active roster. The 24-year-old has slashed .245/.286/.528 in 57 plate appearances with the Padres this season, and his OPS is 1.022 at Triple-A. Should the Padres run into any problems with infield depth in the future, Rosario would be a likely candidate to rejoin the big-league squad.