Kohn, 25, yielded a pair of homers in Tuesday night's series opener against the Rangers at Angel Stadium. He's 0-1 with a 7.30 ERA in 14 appearances.
Highly regarded as a back-end reliever coming into the season after a solid 2010 performance, Kohn has some early command issues and was sent to Salt Lake. He appeared to iron things out in the Pacific Coast League and rejoined the Angels on June 20.
Kohn has been hurt by the long ball. After giving up just five home runs in 107 Minor League games, he has yielded six in 12 1/3 innings among 14 hits allowed. He has nine strikeouts against nine walks.
"Michael Kohn is in about the same boat as [catcher] Hank Conger [who was sent to Salt Lake on Tuesday]," Angels manager Mike Scioscia said. "He has terrific upside, but he really needs to clean some things up.
"His first issue is fastball command. As he commands the fastball better, he can command counts better and put hitters away. He needs a more consistent breaking ball. With his breaking ball inconsistent, he has to get back in counts with his fastball.
"He's showing signs he can make strides. His upside is definitely the back end of the bullpen."
Kohn had a 2.11 ERA in 24 appearances last season, going 2-0. His fastball velocity was up this year, but location has been his undoing.