Mazzaro was called up by the Giants on Saturday, CSN Bay Area's Alex Pavlovic reports.
He'll take Mike Broadway's spot in the bullpen after Broadway was sent to Triple-A Sacramento on Saturday. The veteran righty reliever posted a 3.75 ERA last year with the Marlins, although he has never been overpowering. His 0.64 ERA in 14 innings with Sacramento likely prompted the promotion, but he is unlikely to see high-leverage looks with the big club.