The Total QBR metric we've consulted in evaluating quarterback play can be tweaked to account for strength of opposing defense.
Alok Pattani of ESPN's analytics team passed along information showing how these adjustments would affect QBR rankings for the 36 quarterbacks with enough plays to qualify for consideration.
Seattle's Russell Wilson and St. Louis' Sam Bradford joined Detroit's Matthew Stafford as the biggest winners in terms of ranking spots gained. Each would move up three ranking spots if opponent strength were factored.
Wilson jumps from eighth to fifth, moving past wild-card playoff opponent Robert Griffin III. Griffin moved back one spot to No. 7.
The chart shows the changes for qualifying NFC West quarterbacks, plus Griffin and Andrew Luck, who are competing with Wilson for offensive rookie of the year. The numbers suggest Griffin and Wilson are interchangeable from a production standpoint.
Fifty is considered to be an average QBR score. The max is 100. Peyton Manning led the NFL in unadjusted QBR (84.1) and defense-adjusted QBR (82.5). The New York Jets' Mark Sanchez ranked last in both at 23.4 (unadjusted) and 22.1 (adjusted).
MVP-caliber quarterbacks tend to be in the 75-plus range.
Arizona's quarterbacks did not have enough plays to qualify in the broader league rankings. However, the defense-adjusted QBR scores for Kevin Kolb would have been lower (38.0 to 33.5). They would have been higher for John Skelton (13.9 to 14.2), Ryan Lindley (9.8 to 11.5) and Brian Hoyer (37.7 to 44.2).
Note that San Francisco's Colin Kaepernick had enough plays to qualify for consideration. He was third in the NFL this season. Kaepernick rises to second behind only Manning when considering only production as a starter.
The move to replace Alex Smith with Kaepernick remains a sensitive subject. The 49ers have opened themselves to criticism if the team fails to reach the Super Bowl. However, the numbers suggest Kaepernick is doing at least as much to help the 49ers win. One question, I suppose, is whether those contributions cost the team in other ways, specifically in relation to style of play. That is a tough one to answer.