He replaces right-hander Kirby Yates, who was optioned to Durham following Tuesday's win over the Blue Jays.
Dominguez had one save in two appearances at Durham this season. He had a 6.14 ERA in 14 relief appearances for the Los Angeles Dodgers in the 2013 and 2014 seasons, his only major league experience.
With right-hander Erasmo Ramirez coming out of the bullpen to start against Toronto Wednesday, the Rays needed relief help. Yates, who threw 43 pitches over two innings Tuesday, would not have been available.
Dominguez, who was acquired from the Dodgers last November, becomes the eighth rookie on Tampa Bay's roster.
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