Kyle Terada-USA TODAY Sports

The San Francisco 49ers' defense limited Adrian Peterson and Vikings in their season-opening win Monday night.

The 49ers' defense was able to throttle the Vikings for most of Monday night's season-opening win with a whole new look.

SANTA CLARA, Calif. - The 49ers defense, with an entirely new coaching staff and group of players, was playing like not much changed in the offseason.

That group that finished ranked fifth in the NFL in 2014, stifled the Vikings in the 20-3 win Monday night, keeping Adrian Peterson's crew out of the end zone and scoreless until the fourth quarter.

"I was very proud of our defense's performance," head coach Jim Tomsula said afterwards. "Eric Mangini and the defense staff, I felt like it was a well-called game, it was a good game plan. And we're happy bout that. We've still got a lot of work to do."

Peterson was held to 31 rushing yards on 10 attempts, while catching three Teddy Bridgewater passes for 21 yards. In total, Bridgewater completed 23 of 32 for 231 yards with an interception, and was sacked five times. Two of those sacks came from 49ers safeties.

Tomsula did his best to temper expectations after the game, despite such a strong performance from the group that saw a number of key pieces leave in the offseason.

The 49ers lost linebackers Patrick WillisJustin Smith and Chris Borland to retirement, and released Aldon Smith in August. 

The most telling statistic of the night: the Vikings finished 1 of 9 on third-down conversions. They struggled to find consistency in the running game, leading to third-and-long situations throughout the night, playing into the hands of Mangini's blitz heavy defense.

"I couldn’t really get into a rhythm. Offensively, we couldn’t keep the drives going," Peterson said.

It didn't hurt to have three-time All-Pro linebacker NaVorro Bowman back in the fold, either. It was Bowman's first regular season game since suffering tearing his ACL and MCL in the January 2014. He was credited with seven tackles, one shy of the team leader, safety Antoine Bethea. Both players had a sack.

"I've been saying since day one, we have a lot of variety in this defense and no matter what the offense is doing, we have an answer for it," Bowman said. "(Mangini) trusts us to take on everything that he's been throwing at us. And, some defenses can't handle the bulk of it. We've done a great job as a group with understanding what he's trying to accomplish and executing it out there on the field."

The Vikings were without starting center John Sullivan, which likely played a significant role in the offense's struggles. Mangini dialed up blitzes throughout most of the game, sending different players at different angles. Minnesota appeared unable to adjust.

A new wrinkle, which was seen in the preseason, was having rookie safety Jaquiski Tartt play a rover position in obvious passing situations. Tartt moved in the box and also played deep in coverage. He notched his first career sack in the first half.

"He’s fast, he’s big, he’s strong, he’s got good cover skills, he’s smart, he works at it," Mangini said. "With all those things, you want a player like that to have a role on the defense and it gives you flexibility. You saw him a couple times where he was down and dropped deep. It’s a three-safety defense now and you can do anything you want with those safeties."

Tartt was an under-the-radar draft prospect in the spring, coming out of Samford. The 49ers took him in the second round and are excited about his future, given the strong start to his pro career. He was third on the team with four tackles in his debut, spending most of his time that hybrid role in passing situations.

"It’s like a dream come true," said Tartt. "I get to blitz, I get to play the tight end, I do whatever."

Added Bowman: "Me and Jaquiski have been trying to get on the same page throughout camp and he's done a great job. Being as young as he is, trying to learn as much as coach is asking to learn with going back to safety and coming up playing in the box, that's a challenge for a rookie."

The 49ers also decided on a Kenneth Acker as their starting cornerback opposite Tramaine Brock, with second-year players Dontae Johnson and Jimmie Ward working into the lineup in nickel situations. 


Chris Biderman is the Editor-in-Chief of Niners Digest and covers the 49ers from their headquarters in Santa Clara. Chris has been writing about the team since the spring of 2013. The Ohio State alum received his Journalism degree in 2011 and has been working in sports media since 2008. Chris, a Santa Rosa, Calif. native, is also a contributor to the Associated Press covering sports throughout the Bay Area. You can follow Chris on Twitter here.

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