Bray was on the DL earlier this season with a strained left groin that bothered him during Spring Training. He returned to the Reds on June 22.
"It's probably all related," said Reds manager Dusty Baker. "Like that old song, 'The ankle bone is connected to the knee bone, the knee bone is connected to the hip bone.' Sometimes when one thing happens to something, you end up favoring something else."
Bray has made nine appearances since his return. In just six innings since coming off the DL, Bray has struggled to find the strike zone, allowing one hit but walking 11 batters.
The southpaw has tallied 14 walks in as many games this season, after surrendering 17 walks in 79 games all of last year.
"Hopefully we can get him right and have him down the stretch," Baker said. "Right now, we only have one left-hander in Marshall out there. We're doing the best we can to mix and match and just try to win as many ballgames and finish as strong as we can."
The Reds recalled right-handed reliever Todd Redmond to replace Bray on Tuesday and designated fellow righty Andrew Brackman for assignment. Redmond was viewed as bullpen insurance after starter Mike Leake lasted just 1 2/3 innings on Monday.
"Our bullpen is big-time short [Tuesday]," Baker said. "It would have been even shorter without Redmond here, who's a starter who can give us some innings."
Redmond's spot may be on jeopardy though, as the Reds acquired closer Jonathan Broxton from the Royals on Trade Deadline day. Broxton is expected to arrive in Cincinnati on Wednesday.