Bailey had to skip a planned workout in the bullpen because of the soreness. The setback meant he won't come off the disabled list on Sunday and start the final game of an interleague series against the Kansas City Royals.
"The last couple of days there's been some soreness in some places [in the shoulder] where I usually don't get soreness," Bailey said. "What we're going to do is evaluate it and go from there."
The 24-year-old pitcher went on the 15-day disabled list May 24 after a medical test found inflammation in the right shoulder. He declined to get a cortisone injection to help the healing.
He made his first start on a rehabilitation assignment Tuesday for Triple-A Louisville and felt no pain. He threw 87 pitches in 4 1/3 innings, giving up six hits and five runs.
When he played catch a day later, he felt soreness in different parts of the shoulder than where it had been inflamed. The Reds tentatively planned for him to throw in the bullpen on Friday and perhaps start on Sunday against the Royals. Instead, rookie Sam LeCure will again take his place.
Bailey said it's not clear why the shoulder reacted the way it did.
"It's just a little bit of soreness in places where I don't get sore, so it was a little bit alarming for me," he said.