The Padres optioned Reyes to Triple-A El Paso on Thursday.
Reyes was one of nine players assigned to the minors or placed on the injured list as the Padres trimmed down their active roster to 25 men ahead of Opening Day. The 25-year-old will move up a level to begin 2019 after tallying 49 strikeouts and a 3.00 ERA in 39 innings at Double-A San Antonio last season.