It was Bray's second attempt at a rehab assignment. He pitched one game for Triple-A Louisville before being shut down with back issues. He had been throwing lately at the team's complex in Goodyear, Ariz.
Even without Bray, Nick Masset and Ryan Madson, the Reds' bullpen entered Saturday leading the National League with a 2.43 ERA.
"Don't ask me what we're going to do," Reds manager Dusty Baker said. "You can never have enough pitching."
Bray is also scheduled to pitch for Dayton on Monday. His rehab assignment can last up to 30 days, so it's too soon to identify a role.
"I'll worry about that when he gets here," Baker said. "I want him to get well now vs. being worried about what he's going to do when he gets here. We want the Billy Bray that we know."