Herrmann, 27, has struggled offensively, hitting .156/.239/.281 with a homer, three doubles and eight RBIs in 25 games. He'll go to Rochester where he'll get more playing time as their regular catcher.
"Chris has done a nice job improving on his catching and we've been happy to see that, but unfortunately with the limited amount of at-bats it's been tough for him to get on track," Twins manager Paul Molitor said. "That's what happens when you don't get to play very often and so we'll try to get him going."
Fryer, 29, is known for his defense, but was also having a nice year offensively, batting .299/.385/.354 with a homer, six doubles and 16 RBIs in 51 games. He was also on the U.S. Roster for the Pan American Games, but will join the Twins instead.
"Fryer's had a really nice year. We've had him here a couple times the last couple years. We had to pull him off the Pan Am Games, but it'll give a chance to come up here and play a little bit."
Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, follow him on Twitter @RhettBollinger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.