Mike Zimmer remains Mike Zimmer, moves during Vikings opener indicate

There's nothing like the first week of the NFL season to bring about a lot of new impressions and big opinions. With that in mind, let's take a look at the NFL's opening Sunday, with thoughts on the Vikings and other teams around the league:

• There was considerable talk about the Vikings offense coming into the season given their $84 million investment in Kirk Cousins and the return to health of promising running back Dalvin Cook.

There was also plenty of chatter about the special teams, with the one positive in a shaky preseason on that front being the strong leg of rookie kicker Daniel Carlson.

But if the Vikings' 24-16 victory over San Francisco in Sunday's opener showed us anything, it's this: Coach Mike Zimmer made his living and reputation — not to mention won a lot of games — by trusting his defense above all else. And he's not about to stop now even if he has some fancy new tools at his disposal.

With two different chances to send Carlson out for long field goals within his range — once on the opening possession of the game and once while the Vikings nursed an eight-point lead in the fourth quarter — Zimmer opted for punts and field position.

And with the opportunity to go for the kill on fourth-and-1 in the closing minutes, Zimmer would only commit to sending the offense onto the field for an attempt to draw the 49ers offside (which actually worked, for the first time in history).

The result? The 49ers had a chance to tie in the final two minutes … but the Vikings defense forced the game-clinching turnover. It's hard to argue with results.

• If the NFL is trying to clean up helmet penalties, a big one was missed Sunday. After Xavier Rhodes made a splendid interception of Jimmy Garoppolo, he was crushed in the helmet by 49ers tight end Greg Kittle. It was as egregious as many targeting penalties called on defensive players, and luckily for the Vikings Rhodes was able to return.

• The 49ers are going to miss injured former Vikings running back Jerick McKinnon. If he hadn't been lost to a torn ACL, he would have given them a playmaking dimension. And watching Alfred Morris fumble on the goal line was a reminder that McKinnon has just three career fumbles.

• Two popular sentiments from the analytics world before the season started were that Buffalo is going to be really bad and that the Saints defense is due for a regression this season after improving in 2017.

One week is a small sample size, but so far both of those things seem to be true.

The Bills trailed the Ravens 40-0 midway through the third quarter — no, that's not a misprint — with everything from turnovers to poor offensive line play to poor quarterback play to awful defense sharing the blame in the misery.

• If you're tracking ex-Vikings: Case Keenum had three touchdown passes (and three interceptions) in a 27-24 win over Seattle in his Broncos debut.