Keys to the season

1. Bradford needs to fit in — and do it quickly

The addition of Sam Bradford salvages the Vikings' Super Bowl hopes after they appeared to be ruined following Teddy Bridgewater's knee injury. No, the Vikings aren't better off with Bradford. But if he can pick up the offense quickly, avoid back-breaking mistakes and make a few big throws a game, they have a chance, albeit slimmer, to go all the way.

2. Bradford is going to have to stay healthy, too

If Bridgewater needs advice on bouncing back from a torn ACL, he can reach out to his replacement. Bradford tore his left ACL in 2013 and again in 2014. He hasn't started 16 games in a season since 2012. So there was risk in the Vikings choosing to acquire Bradford. They can potentially weather injuries to a few starters at once. But they can't lose another starting quarterback and survive.

3. Mike Zimmer's defense has to take another leap

Star Tribune, Star Tribune

The Vikings could very well have a competent offense if Bradford fits well in Norv Turner's scheme and if their offensive line is better. But their biggest strength is Zimmer's deep, talented, athletic D. If Anthony Barr, Xavier Rhodes and Sharrif Floyd can stay healthy and become top players at their positions, and if Eric Kendricks, Trae Waynes and Danielle Hunter ascend, too, look out.

4. Adrian Peterson must stiff-arm Father Time again

Peterson, now 31, showed no signs of slowing down last season when he led the NFL in rushing yards despite having to dodge defenders in the backfield far more often than the Vikings would have liked. They will have to lean heavily on him again this season. But when it comes to 30-something running backs, they usually don't see Father Time coming out of nowhere to clothesline them.

5. Blair Walsh will have to make a few clutch kicks

Walsh has said all the right things about moving on from his infamous gaffe in the playoff loss to Seattle last January. And he had a solid training camp and preseason. But we won't know if Walsh has truly recovered from "wide left" until he drills critical kicks in tense moments in 2016. They're coming.

Matt Vensel