Fiers (elbow) will make a rehab start for Triple-A Las Vegas on Tuesday, Matt Kawahara of the San Francisco Chronicle reports.
Fiers missed the start of the season due to hip inflammation and returned to make just two starts before hitting the injured list with a sprained elbow. The Athletics believe he has a chance to return before the end of the season, but he's unlikely to make very many appearances if that does end up happening.