After swinging at strike three, Torrealba immediately began a heated argument with Dario Rivera Jr. over a previous strike call during the at-bat.
Roughly 15 seconds into the exchange, Torrealba struck the umpire in the mask.
It's unclear what type of punishment Torrealba, a member of the Leones del Caracas squad, will face from the Venezuelan League or from the Rangers.
"We don't have all the details yet but will look into it," Rangers general manager Jon Daniels told ESPN Dallas.
Torrealba hit .273 with with seven home runs and 37 RBIs for the Rangers last season.