Pena agreed to a contract Jan. 12 with CTBC Brothers of Taiwan's Chinese Professional Baseball League, CPBL Stats reports.
Pena was reassigned to minor-league camp Saturday.
Pena belted a two-run home run in his one at-bat during Monday's Cactus League loss to the Royals.
Pena signed a split contract with the Reds on Tuesday that will pay him $600,000 if he makes it to the big leagues during the 2021 season, Bobby Nightengale of The Cincinnati Enquirer reports.
Pena will be a part of the Reds' 60-man player pool this season.
Pena signed a minor-league contract with the Reds on Saturday, C. Trent Rosecrans of The Athletic reports.
Pena was traded from the Cardinals to the Giants on Thursday for cash considerations, Maria I. Guardado of MLB.com reports.
Pena (oblique) will start behind the plate and bat fifth Saturday in the Cardinals' Grapefruit League game against the Nationals.
Pena (oblique) should return to action for Saturday's spring game against Washington, Ben Frederickson of the St. Louis Post-Dispatch reports.
Pena (oblique) could be cleared to return to the Cardinals' Grapefruit League lineup by the end of the week, Jenifer Langosch of MLB.com reports.