That's true, but it's job to field the best team possible (with all things considered).
Carson was a gamble that, if it paid off, would have given us a franchise QB for years to come. We know Frank vouched for him and thought he could 'fix' his issues.
A lot has been written about how he wasn't a leader, a good fit in the locker room, etc., but until that comes out of the players mouths it's all second hand gossip.
What you have to admit is that Ballard made the best of that whiff, he essentially traded Ryan for Carson without losing a draft pick and got him at a better salary.
As far as Rock, yes he was starting to come on. But I'll take a proven edge rusher over a proven CB every time.