NASHVILLE – There was frustration — but not fluster — as the Vikings defense huddled around coach Mike Zimmer at halftime in the locker room at Nissan Stadium.

The Tennessee Titans, using more misdirection than a Las Vegas magician, had just pieced together a 13-play touchdown drive late in the second quarter to seize a 10-0 lead over the reigning NFC North champions. By the time they had stomped their way into the locker room, the Vikings had five, maybe six minutes to make adjustments.

There was no frantic scribbling on a whiteboard or any fiery speeches from the head coach. Instead, Zimmer and his assistants showed his defenders how a few busted plays had gone wrong and simply told them that he wanted to scale things back.

“We weren’t reeling. We felt good about where we were,” linebacker Chad Greenway said after the Vikings rallied for a 25-16 victory. “It was just getting back to our base calls and playing ball.”

In other words, it was time to stop worrying about all the smoke and mirrors from the Titans and to start imposing their own brand of “exotic smashmouth” on defense.

Thanks to a dominant second-half performance from Zimmer’s deep and talented defense and a tide-turning pick-six by linebacker Eric Kendricks, the Vikings on Sunday avoided a second consecutive season-opening upset at the hands of an inferior opponent. They scored two defensive touchdowns in a game for the first time since 2007 and put 25 consecutive points on the scoreboard as they cruised to victory.

Danielle Hunter scored on a fumble recovery early in the fourth quarter for the Vikings, who won despite Adrian Peterson being held to 31 rushing yards and Blair Walsh missing a pair of field-goal attempts and an extra-point try.

Veteran quarterback Shaun Hill, who got the nod over newcomer Sam Bradford, only needed to be solid. The 36-year-old was, throwing for 236 yards with no turnovers a dozen days after starter Teddy Bridgewater suffered a season-ending knee injury.

The Titans had Zimmer’s defense on its heels throughout the first half. Using an array of formations, personnel groupings and pre-snap motions, they kept the Vikings guessing with designed runs for quarterback Marcus Mariota, full-house formations with runners DeMarco Murray and Derrick Henry both in the backfield, a Wildcat run with Mariota standing on the sideline, and a bunch of deceptive play-action passes.

“They had us off balance,” Zimmer admitted. “They were doing a lot of shifting, motions, line up here, run guys in, run guys out, run guys in the flat, run guys the other way. You know, you prepare for it but it’s unnerving a little bit.”

That preparation was made difficult because the Titans, who won a total of five games over 2014 and ’15, have a new offensive coaching staff and many new additions on that side of the ball, including two big linemen and a pair of bruising backs in Murray and Henry, last year’s Heisman Trophy winner. The buzzwords bandied about by Mike Mularkey, in his first full season as Tennessee head coach, were “exotic smashmouth.”

Zimmer and the Vikings figured the Titans planned to combine power running with plenty of misdirection. But they weren’t exactly sure how it was going to look.

“They saved a little bit of their gimmicks, their tricks for us,” Kendricks said.

With Mariota making quick, smart decisions on the move, the Titans rolled into Vikings territory on all four of their first-half drives. The Vikings were able to limit them to three points on their first three drives. But the home team took a 10-0 lead into halftime after Mariota tossed a pass in the flat to Murray, who soared over cornerback Terence Newman and into the end zone for a 6-yard touchdown.
Moments later in the locker room, Zimmer quickly simplified his defensive game plan.

“They made some plays on some stuff that we hadn’t really seen. Some of it they got to it in different ways. It was a process to come in and see what they were doing,” Greenway said. “Luckily, we held them to 10 [points], so we knew we were in the ballgame. There was just no panic in here. We knew we just had to get something going. Eric’s play, obviously, was the catalyst. Then things just snowballed in our favor.”

For nearly three quarters Sunday, Mariota could do no wrong. During a flurry of keepers and play-action passes, Mariota hadn’t made a bad decision, whether he was moving the chains on third down or smartly aborting bad plays with throwaways.

With the Titans up 10-6 and threatening to expand their lead, he made his first critical mistake of the day as defensive end Everson Griffen bore down on him. Mariota tried to force a pass to wideout Harry Douglas. Kendricks was lying in wait and pounced, returning the interception 77 yards for a go-ahead touchdown.

“It was a hard play-action [fake],” Kendricks said. “I thought it was going to be a run play. As soon as I saw Everson go upfield, I knew he had the ball and I just trailed my guy on his hip. I knew he either had to get sacked or throw the ball.”

In hindsight, Mariota probably would have preferred to get pummeled by Griffen.

The Vikings ran away with it from there, thanks to Hunter scoring on a 24-yard dash after scooping up a Mariota fumble, to open the 2016 season with a win. They allowed Tennessee to gain only 122 yards in the second half, 59 of which came on a late-game scoring drive when the outcome was essentially already sealed.

“It shows the resiliency of this football team,” Zimmer said. “They have been through a whole lot [the past couple of weeks]. … So we’ve got some fighters in this crew.”

Matt Vensel is in his third season covering the Vikings for the Star Tribune. matt.vensel@startribune.com