The move gives the Twins another backstop along with Drew Butera, who started behind the plate for the third straight night. Mauer is out with back spasms while Doumit is dealing with a strained oblique.
"[Herrmann's] here to protect us a little bit," Twins manager Ron Gardenhire said. "Doumit is feeling better, but he's still a couple days away. He said he's ready in case of an emergency, but we need the protection with two guys hurt."
Herrmann, 24, hit .276/.350/.392 with 10 homers, 25 doubles and 61 RBIs in 127 games with the Rock Cats. He stayed fresh after the end of the Minor League season by catching Twins prospects at the club's Spring Training complex in Fort Myers, Fla., for the last two weeks.
"He's a really athletic kid," Gardenhire said. "He can play left field and is really versatile. He's got a really nice swing and can hit. And he can catch and throw. He's quick. I'm anxious to see him. He did well at Double-A and is moving right up the ladder."
Mauer has been out since Monday, but he's getting closer to making his return, according to Gardenhire.
"He did some work today," Gardenhire said. "He took some throws from second and hit in the cage. He feels better, but he's not ready to play."