I can't give Wolf much credit for Kurt Warner. He was never a backup QB for the Packers. Wolf signed him as a undrafted rookie and cut him shortly thereafter (I don't think he even made it to training camp). Warner bounced around for 4-5 years coaching and playing in the arena league before finally making it to an NFL roster.
Best backups in the history of football? I can't agree with that. Bratkowski was better when he backed up Starr. Earl Morrall has often been called the best backup ever. Steve Young backing up Montana for four years. I think there were a lot better ones than the likes of those that Wolf had. (Heck, how about that kid who backed up Favre his last seasons in GB? )