I'm convinced the real reason Flood refuses to give Rettig a shot is because he knows if Rettig does do well it would likely lead to his firing since it'll show he doesn't have good judgement for the most important position
'Ya know, I've thought this as well; that if Rettig did come in and somehow light it up, it would make Flood's decision making even more suspect. (Which, in itself, would be quite an accomplishment.)