The Twins are set to play without a designated hitter for the next five games, with a two-game series starting on Tuesday in San Diego against the Padres and a three-game set that starts on Friday in San Francisco against the Giants.
Gardenhire wanted another bat on his bench with the pinch-hitting and double-switching that comes with playing without a DH. So the Twins went back to a 12-man pitching staff and called up Herrmann, who had been swinging a hot bat since being optioned to Rochester on May 8.
Herrmann hit just .128 in 15 games with the Twins, but he batted .400 (14-for-35) with a homer, three doubles and a triple in nine games with the Red Wings since getting sent down.
"We'll get him back in the fold," Gardenhire said. "He's been swinging pretty good down there. It gives us an extra guy off the bench, which we desperately need. With pitchers hitting, it's something we're not used to."
Tonkin, meanwhile, has been struggling recently and has a 5.84 ERA on the season after giving up eight runs (six earned) over his previous four relief appearances. But he fared better against the Mariners on Sunday, throwing a scoreless eighth inning.
Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. This story was not subject to the approval of Major League Baseball or its clubs.