Leake's move is retroactive to Wednesday but the 22-year-old could return for the post-season, the Reds said on Friday.
"It's better for him, and he still may be eligible for the playoffs," manager Dusty Baker told the team's website (http://cincinnati.reds.mlb.com). "He's not throwing the ball where he wants to throw it, even though he has good velocity.
"We had to do something with him anyway. This way we'll get him on a strengthening program. He can focus on that and not on pitching. Now is the time to do it."
Leake has gone 8-4 with a 4.23 ERA in 24 appearances this season, including 22 starts. He has thrown 138 1/3 innings since making his debut in the majors without pitching in the minors.
(Editing by John O'Brien)