Geno Atkins destroyed another game plan on Sunday.

SANTA CLARA, Calif. - Nose tackle Domata Peko said after his defense had held a foe to two touchdowns or less for the sixth time in the last seven games Sunday at Levi's Stadium that a quarterback's best friend is a good running game and a good defense.

In the 24-14 victory over San Francisco, the defense went right from friends to loved ones when they gift-wrapped AJ McCarron's first NFL start with four turnovers, four sacks,  and a suffocating performance that didn't yield a third-down conversion until less than three minutes left in the game.

The old dog-eared cliché is that everyone else has to step up their game when the quarterback goes down, but the defense turned it into poetry with supreme days from their best players. With the offense struggling to produce a season-low 242 yards against the NFL's third worst defense, they needed all the heroics:

-WILL linebacker Vontaze Burfict played a heavy dose of nickel for the first time all season and logged his most snaps in his eighth game back from micro fracture knee surgery with 65 and responded with his first sack and first interception of the season.

-Pro Bowl nose tackle Geno Atkins, playing a backup guard for the third time in a month, destroyed yet another game plan with two sacks and a tackle for loss while forcing four holding calls to give him double-digit sacks (10) for the first time since 2012.

-Cornerback Adam Jones, who has missed the only two games the Bengals have allowed more than 14 points since Nov. 1, returned to the lineup with an interception, could have had two, and when he dropped back to return punts for the first time in more than a month his very presence set up a TD with an 18-yard shank. The passing game was never a threat with Niners quarterback Blaine Gabbert averaging fewer than six yards per his 50 passes.

"Everybody is playing together. Nobody is pointing fingers," Burfict said. "If you mess up, you say it's your fault. Next play you make up for it."

The Bengals have made up for enough of them that with two games left the Bengals have allowed 243 points, 41 points away from the club's fewest allowed in a 16-game season with 284 in 1978.

"We came into the game as a defense saying we wanted to put our offense in the best field position," said left end Carlos Dunlap, who got it all started with one of his patented strip-and-run fumble returns. "We came into the game with the mindset that we wanted to make it easier for A.J. over there at quarterback."

Dunlap agreed that it was his play that got everything going. In a scoreless game in the middle of the second quarter, the Niners looked like they had converted a third-and-10 at their 32 on a 12-yard pass to wide receiver Anquan Boldin, one of the most physical receivers in the game. Dunlap, who had rushed Gabbert, quickly closed on Boldin, wrenched the ball free as they went to the ground, got up, and took it 21 yards the other way to the Niners 11 to set up the game's first touchdown.

"I saw the way he was carrying the ball and it was an opportunity to make a play," Dunlap said. "We weren't driving the ball as much as we wanted on offense. Right there that put them in great field position and we lit it up from there."

Indeed, the Bengals offense that had just two first downs until that play scored three touchdowns in the final 5:16 of the first half for a 21-0 half-time lead that broke it open on drives of 11, 36, and 20 yards. And looking back on it, Dunlap thinks he could have scored that first one himself.

"I thought they blew it down," Dunlap said of the whistle. "So I was in between. That's why I didn't score. If I had known at that moment, yeah. I like my odds."

And you have to like the odds when Burfict goes into the nickel package on passing downs. The Bengals were trying to ease him back into things and get him ready for the playoffs by playing him mainly on first and second downs, limiting to him about half the snaps.

Well, defensive coordinator Paul Guenther knows now is the playoffs. Particularly after the Steelers converted eight of 14 third downs last week.

"What was the percentage?" Burfict asked and told it was two of 14 with a goose egg until less than three minutes left, he smiled.

"Damn, that's pretty good. I guess when I'm in nickel we're pretty good."

Burfict, who said he was inspired by Sunday's early play of another Pro Bowl linebacker coming back from a devastating knee injury, the 49ers NaVorro Bowman, said he basically played the tight end man-to-man in those packages. And it was his coverage of Vance McDonald that turned into the back-breaker.

Leading 14-0 in the last minute of the half, Burfict was in nickel on second-and-10 from the Niners 33 and he and cornerback Dre Kirkpatrick were on the case.

"I had corner help outside me. I allowed (McDonald) to go to the corner and Dre hit him and the ball popped up," Burfict said. "It was so slow and I thought, 'Can I jump for it?' "

He could and his 16-yard return put the ball on the 20 and it took McCarron just one play to cash it for the 21-0 lead on the 20-yard touchdown pass to rookie tight end Tyler Kroft.

Just moments before in a 7-0 game in another nickel situation, second-and-eight from the Niners 22, Burfict set up the shanked punt with a blitz off a sack. This time he conspired with slot corner Leon Hall to put pressure on Gabbert.

"(Guenther) just didn't want me to show up on the line. He wanted me to come from depth," Burfict said. "The running back looked at me and picked up Leon. Nobody blocked me. Christmas present."

With Niners left guard Alex Boone inactive, Atkins was again naughty with a dominant performance that left coal for a game plan.

"Dude, Geno is a freaking animal, man," Peko said. "We're so blessed in Cincinnati to have one of the best three techniques in the game. He destructed a lot today and when he destructs like that you're able to get Dunlap some sacks and freaking guys like me getting five sacks. Geno sets the tone for our defense. He's a hell of a player."

Peko got his career-best fifth sack, which meant he entertained his mates with his ever popular belly dance. The idea behind it is that he's earning his keep so he can eat.

But Sunday left one of the franchise's best defenses a little hungrier.

"We gave up those two late scores and that made us mad," Peko said, "when we're one the toughest scoring defenses in the game. That's good. You don't want people to get complacent. You want to try and get better."

Thanks to the defense. This one got out of the way early. It was 24-0 in the middle of the third quarter. Plenty of time to think about the trip to Denver on Monday night. A December Super Bowl. The winner gets a bye.

"We're not there yet," said Burfict when asked about five straight post-season berths. "My mind's on the next game."