It's not really a matter of casting blame. I still think the Manuel pick was the right thing to do even with the benefit of hindsight. It's not as if some better qb was out there (it was a bad draft), and the draft overall was pretty lousy. https://en.wikipedia.org/wiki/2013_NFL_Draft
More to the point, though, Whaley was really, really high on Manuel. He saw him as a Big Ben type. He was wrong, of course, but everyone makes mistakes. I don't fault him for it, really.
Who was really worth taking at 16? Maybe Xavier Rhodes, but they were pretty solid at CB at that point. Maybe Eifert, but the Bills don't draft TEs early. Maybe DeAndre Hopkins, but as many have said here, that's putting the cart before the horse (they had no real qb). Other than that, there isn't much in the latter half of the first round that stands out.