The Nationals selected Ribalta's contract from Triple-A Rochester on Tuesday, Andrew Golden of The Washington Post reports.
It's the first major-league promotion for Ribalta, who earned it after holding a 2.58 ERA and 67:22 K:BB over 45.1 innings between Double-A Harrisburg and Rochester. The 26-year-old reliever was a 12th-round pick of the Nationals back in 2019.