I agree with most that our division will be the biggest threat.
At first, I want to say the Whiners are the biggest challenge, and I think they still are, but they will drop off. No Bowman and questions at WR (Crabs and Boldin aren't enough to get it done, and Kaepernick hasn't proven he can work with 3 options yet) will hurt them a bit, but they're still a damned good team.
The Cards could be scary, Palmer got better in Arians' system the last half of last year, they're getting Honeybadger back, and they're defense is really really good. They've addressed the their biggest question mark which was the OL; if Palmer gets time to go vertical, he still can and that can be a great team. Thing is, if they want to take the division, they have to beat SF, something which they've failed to do the last 10 or so times they've played.This division is going to be so good, that if a team gets swept by a division rival, that's probably going to do it for them. I fully expect 3-3 to win this division.
I'd have to say the next team would be the Saints. They really improved their defense, and we had a tough time running on them already. They've gotten much better in the secondary and that's where we beat them. They already had a better offense than us, and the addition of Cooks will make them tough to scheme against. If they have to play us up here, we still beat them but if we play them there....they could win and it's not a long shot. Thing is, their division just might be the next best division in the NFL. Tbay will be a tough out and Carolina seems to play the Saints well recently. Throw in Atlanta, who also plays the Saints tough....and they won't have the rash of injuries they had last year. That was freakish.
If I had to pick the next one, it would be a toss up between Chicago and the Eagles. The Eagles run the ball well, which is actually our weakness. Both teams will have to improve a ton on defense to compete with us, but they did both go heavy on defense in the draft.