Statistically rankings of DBs are imperfect. The above approach is an interesting methodology, being that is based on passer rating “when targeted.”
But if a DB is truly a shut-down DB, the WR he is matched against may rarely get targeted (even if that WR is the best on the opposing team). And, presuming the best DB is matched against the best WR, the stats may be misleading because the best WR will catch difficult passes that a lesser WR cannot catch. I am not disputing that JJ is one of the team’s best, but due to the many variables, a pure statistical ranking of DBs is not a perfect gauge of who is best.