http://www.pro-football-reference.co...Vi00/gamelog//
look at 2007 - Tenn wins 9 games with VY at the helm - in 5 of those games he doesn't throw a TD pass, his QB rating is below 60 in those 5 games and the defense holds the other team to 13 points or less - in 3 games the other team doesn't get 10 points.
We had six wins last season and Fitz was never below a 78 passer rating in those wins. If he has a game like VY did in any of these five wins - we most likely lose those games - perhaps we beat Washington or Denver but the other 4 games are sure losses.
VY was very often carried by his team. Ditto Tebow last year.
So to the OPs question - why can't you count wins and losses to the QB? - you can, if he is the reason they win or lose. Citing Kelly and Montana and co, you have to consider the team they were on - compare Fitz's numbers in his first year as a named starter in camp, and he comes out pretty well against a lot of folks.
With all stats, you have to look at them in context - in nearly 1/3 (10) of VYs wins, his rating was below 70 - with Fitz, only one time did he have a rating below 70.
In VYs wins, he averaged barely over 1 TD per game - in Fitz' wins, it is nearly 2 a game.