The best measurement of a quarterback is how they fared against a defense relative to all other quarterbacks that also faced that defense. That removes the impact of schedule strength, because the highest game allowed by a great defense may seem average were it against a weak secondary.
The top-8 fantasy performances against each defense were arrayed and each quarterback was recorded for how often their fantasy points were in the top-8, the top-4 and highest allowed versus that specific defense last season.
Adding up those numbers yields a “better than average” (BTA) score since they are better than the average quarterback that faced a defense. It also weights the performances since a first place counts as a top-4 and a top-8.
