"He's just not feeling great," Reds manager Bryan Price said.
The Reds are not planning to shut Bailey down yet, but haven't ruled it out.
"We have the right to shut him down, we have not made that decision yet," Price said. "Until we do, you can anticipate that perhaps he may pitch again this year."
Bailey made six starts in his return from Tommy John surgery. In his first four starts, Bailey posted a 3.66 ERA, but struggled to go deep into games, averaging fewer than five innings per game. In his last two, Bailey pitched a combined 3 1/3 innings, allowing 10 runs (nine earned).
Cody Pace is a reporter for MLB.com based in Cincinnati.