User blog comment:FairyRaven/Fairy Tail Chapter 392: You Must Not Forget, Review and Commentary/@comment-98.26.119.147-20140711133319/@comment-5343732-20140711140457

well basically Gray got the steel ball from the rubble and he was harmed from when Gray used Silver's own demon slaying magic against him, it didn't finish him off but still dealt damage to him and finially i assume that a small proportion of the fight did happen off screen, as Silver does say something along the lines of "i've blocked your physical attacks" {mangapanda version} so that explains for the damage caused to Silver