I'm too lazy to do the research, RFIP.
But if I understand your statement challenge correctly, by definition your grouping of "good" QB's is 5-10 deep.
And your grouping of top HC's is 5 deep.
Depends on one's definitions of good in each category then, huh?
For example, there are 12 playoff teams every year. Aren't they all "good"?
Or how about winning QB's and HC's. Aren't there about 16 or so every year?
Know what? I think you've been caught shooting from the hip with your earlier statement.
Just to be clear, I agree that a good QB is very important to a HC's success. Duh!
Can you agree that a good HC can raise a journeyman QB's effectiveness sufficient to achieving a winning season? Maybe even a playoff appearance with an occasional win?