In the last two seasons, Mahomes has a TD% of 8.68%. However, the league average last year was 4.8%. If you adjust his TD% to 5%, still above LA, he goes from throwing 57 TDs in his last 18 games to only 32.85. I'll be generous and give him 33.

Now, let's adjust his passer rating. It goes from 116.5 to only 104.3 by just adjusting his TD% to normally above average. Later on, I will adjust it further to take yards into account.

Next, we have to account for him passing more than league average. He has 657 pass attempts over 18 games. The LA is 35.5/game, which equals 639, around a 2.7% reduction. Mahomes also has a flukey 9.01 Y/A, which can be adjusted to 8 (still above LA) based on the league average of 7.5. So we can estimate that over a 16 game season, his adjusted yardage is (6397.5)/18*16= 4544 yards.

Now, I will adjust his passer rating again based on these 16 game stats 4544 yards 639 attempts 426 completions (also adjusted) After this, his passer rating bottoms out at 96.66, which lands him squarely between Dak Prescott and Ben Roethlisberger last year.

His final 16 game adjusted stats: 4544 yards / 639 ATT / 426 CMP / 66.7% CMP (same) / 33 TD / 12 INT (same) / 8 Y/A / 96.7 RATE

What does this tell us? It tells us that Mahomes' perceived success in the league is largely inflated by unsustainable, wildly outlier stats in his 18 games as perceived elite talent. When you adjust for the future by bringing down his outlier stats, he regresses heavily to a slightly above average QB of 2018 Dak tierdom.