The Arizona Diamondbacks have released left-hander Luke Weaver from their starting rotation. He is expected to fill the fifth rotation spot. Other candidates are Humberto Castellanos, Caleb Smith, and Tyler Gilbert. The Diamondbacks currently have two other major league ready arms at Triple-A Reno. However, Weaver’s presence could change that. The Diamondbacks may decide to keep Weaver in the bullpen.