We are never going to agree on the injury thing, so I'll leave it with this. Admittedly, I'm trolling a bit, but within every good troll is an element of truth.
Part of my reasoning is that I'm talking about a very small difference of 1 to 2 games in a season. I think the Niners were in that 2 games below average area last year. Their biggest losses, IMHO, were McGinley, and Gould.
The more controversial part will be my opinion that the loss of Staley was not significant. I'm not taking away from his legacy when I say that I really don't think he was playing at the same level the last couple of years, granted we didn't even get to see 2 full games before the injury last season.
Another reason that plays into the 2-Horse race is uncommon opponents. AZ gets Detroit and Carolina, arguably the 2 worst teams in the NFC. SF is already a game back, and gets, arguably, the 2 best teams in the NFC, Saints, and Packers. Price of success. The Seahawks are already 1-0 against their uncommons, Atlanta and Minnesota.