On Friday, the Reds placed Leake on the 15-day disabled list, retroactive to Wednesday, and recalled infielder/outfielder Juan Francisco from Triple-A Louisville.
Leake, who is 8-4 with a 4.23 ERA in 24 appearances including 22 starts, was examined by Reds medical director Dr. Timothy Kremchek, who diagnosed the 22-year-old with shoulder fatigue.
"It's better for him, and he still may be eligible for the playoffs," said manager Dusty Baker. "He's not throwing the ball where he wants to throw it, even though he has good velocity."
Leake, who will be eligible to come off the DL on Sept. 9, had thrown 138 1/3 innings since making his Major League debut without pitching in the Minors.
"It's something we're apprehensive about," Baker said. "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's ERA ballooned from 3.78 to 4.23 following two relief appearances.
"His breaking ball hasn't been as sharp," said Baker. "It's been rough on him lately."
Francisco is in his third stint with the Reds this season. He hit .286 with 18 home runs and 59 RBIs in 77 appearances for the Bats. Francisco provides insurance while Laynce Nix recovers from a sprained left ankle. Nix is listed as day to day.
Jeff Wallner is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.