I'd like to post Alex Smith's performance against defenses vs. what those defense allowed against all the other teams they played. Data displayed as % above what defense allowed vs. everyone else:

@ GB: +72%

DET: +22.3%

@MIN: -6.6%

@NYJ: +3.7%

BUF: +85.7%

NYG: -48.7%

SEA: -3.3%

@ARI: +143.6%

Season: +30.5%

Also notice that Smith does not decline vs. better defenses and improve vs. poor defenses, as people would assume based on the Buffalo game:

Smith/Opp

GB 125.6/73.1

DET 107.7/88.1

MIN 81.1/86.8

NYJ 78.1/75.3

BUF 156.8/84.4

NYG 41.0/79.9

SEA 74.5/77.1

ARI 157.1/64.5

All 102.1/78.3

If you exclude the Detroit, Min, and Buffalo games, Smith CLEARLY gets better as opposing defenses get better...which is amazing. Its a steep, tight, negative correlation between Smith's QB rating and the opponents QB rating allowed: the lower the defense's QB rating, the better he does!

***math nerds only: If you throw out those three games, here's what the regression looks like y = -6.5358x + 584.62; R² = 0.7721
with all games: y = -1.529x + 222.88; R² = 0.0842
(still technically significant with all games, but not necessarily meaningful)