METAIRIE — The resurgent New Orleans Saints have displayed textbook passive-aggressive behavior on defense this season, bowing up inside the red zone while readily yielding yards between the 20s.

But if interim coach Joe Vitt and first-year defensive coordinator Steve Spagnuolo can spur their defense to play more like Tarzan and less like Jane in the middle of the field for the last six games, a berth in the “Second Season’’ might become reality.

It’s imperative that the Saints’ defense doesn’t monkey around Sunday at the Mercedes-Benz Superdome because multiple slip-ups could prove costly against the NFC West-leading San Francisco 49ers (7-2-1).

Kickoff is 3:25 p.m.

“Early on, it had nothing to do with the system, guys were just making mistakes on defense,’’ Saints middle linebacker Curtis Lofton said of the team’s 0-4 start. “Guys are still making mistakes, but we’re making up for those mistakes by playing faster. We’re playing instinctively. We’re reacting more and doing less thinking.

“That’s how we’ve been playing these last few games. We’re still giving up yards, but our saving grace is we’re playing great in the red zone, we’re playing better on third down, and we’re getting turnovers.’’

A good example of Lofton’s three-point stance came Sunday in Oakland, where the Saints (5-5) dominated, winning 38-17 to reach the .500 mark for the first time.

The Raiders amassed 404 yards, but 119 came in the fourth quarter after the outcome had been decided. The Saints finished plus-2 in turnover differential, scoring on free safety Malcolm Jenkins’ 55-yard interception return. And the Raiders converted only four of 12 third-down plays, only twice in the final three quarters.

Granted, the Raiders are one of the NFL’s bottom-feeders at 3-7. But New Orleans’ wall-to-wall performance lends credence that the players are becoming acclimated to Spagnuolo’s scheme despite what the stats suggest through 10 games.

Yes, the Saints remain last in total yards allowed per game (462.8) and 27th in points allowed (27.3).

But other key stats show signs of respectability: third-down efficiency (19th in the NFL, 38.8 percent), turnover differential (+2, 12th in the NFL) and goal-to-go defense (inside the 10-yard line), where the Saints rank ninth.

Of 27 goal-to-goal situations, New Orleans has allowed 16 touchdowns (59.3 percent), including all three times in a 34-14 loss at Denver in Game 7.

“We got kicked in the face by the Broncos, but those things happen in this league,’’ strong safety Roman Harper said.

But in other games, the Saints have stood their ground:

  • In Game 6, the Saints turned back Tampa Bay on downs from first-and-goal at the 2, fueled in part by Jenkins’ touchdown-saving tackle of Buccaneers wide receiver Vincent Jackson.
  • In Game 8, the Philadelphia Eagles had four goal-to-go possessions and were limited to two field goals.
  • In Game 9, a dramatic goal-line stand in the final two minutes preserved a 31-27 win against the previously undefeated Atlanta Falcons.
  • And in Game 10, Harper killed a potential Raiders scoring threat with an end-zone interception, spoiling a first-and-goal from the 1.

All four of those games resulted in Saints victories.

“When it comes to tweaking the defense, there has been some give-and-take on both sides — from the players and Spags,’’ Jenkins said. “I think Spags has done a good job of tailoring his defense to the abilities of the guys in this locker room. But, at the same time, he hasn’t compromised the fundamentals of his defense.’’

“When Spags first got here, he only knew us from what he had seen on film,’’ linebacker Jonathan Casillas said. “He didn’t know the ins and outs of our game. Now, I think he’s got a good feel for that. He’s utilizing us and putting us in the right positions to fit his defense.’’

That seems to be the case in the red zone, where the Saints have been particularly stout against the run. In Games 1 and 2, Washington and Carolina combined to score five rushing touchdowns inside 6 yards. Since, the opposition has scored only two rushing touchdowns inside the red zone (13 yards and 1 yard) compared to 16 passing touchdowns inside the red zone.

Denver quarterback Peyton Manning started the trend in Game 7, throwing scoring tosses of 1 and 2 yards in goal-to-go situations. Atlanta quarterback Matt Ryan threw touchdown passes of 1, 2 and 6 yards, and Oakland quarterback Carson Palmer tossed a 1-yard scoring pass.

“We have the mindset that nobody is going to run the ball on us,’’ Lofton said. “To us, it’s like somebody is challenging your manhood when they go for it on fourth down.

“If we stop them, it’s like getting a turnover. As a defense, we got to get the job done in those situations, no matter what. And it’s not always about X’s and O’s. Sometimes it’s about someone running and blowing something up, and that’s what we’ve been doing.’’

If the Saints defense can play with that same goal-to-go mentality between the 20s, they might be good to go for the playoffs.

But that’s a big if.