The bag heads?

Not here. Not now.

While the Louisiana Superdome has long been a classic big-game venue, the New Orleans Saints’ late-season schedule has historically contributed little to the iconic stadium’s lore.

On Sunday, however, two teams that were expected to be fading from playoff contention will play before a sellout crowd in a game with postseason implications.

The upstart 49ers are trying to rebound from a close loss that many thought should have wound up as San Francisco’s fourth-straight victory. As it is, the Niners (5-6) are only one game out in the NFC wild-card race.

But to stay in it, they’ll have to win in the raucous, refurbished Superdome, a stadium now conspicuously devoid of embarrassed fans wearing grocery bags on their heads as the Saints (7-4) have surged surprisingly to the top of the NFC South standings.

“We’ve been playing better football the last month, which is good, but certainly we understand we’ve got a huge challenge this week going into the Saints’ place there,” said 49ers coach Mike Nolan, who should remember the bag heads very well.

It was an awful Saints team coached by his father, Dick, in 1980 that prompted the late Buddy Diliberto, a popular local sportscaster, to recommend that Saints fans wear bags over their heads in protest of a team that lost its first 14 games of the season.

“He had really aged that year,” Nolan recalled of his father. “He had black hair at the beginning of the year and a bunch of gray at the end. It was a tough time. It hurt, as it always does. That was my last memory there, but most of my memories of New Orleans are fond memories.”

New Orleans has had only a few winning seasons since, but 2006 seems to be shaping up as the latest.

“Obviously, they’re playing very well,” Nolan said. “Certainly, offensively, they’re extremely explosive.”

Explosive might be an understatement. Coming off complicated offseason throwing shoulder surgery, Drew Brees is somehow throwing the long ball better than he ever has. He leads the NFL in passing yardage with 3,463.

Leading receivers Joe Horn (groin) and Marques Colston (left ankle) were questionable during the week, even missing a couple practices. But Brees has kept firing when either Horn or Colston have been out in the past month. Last week, it took only three plays for him to hit rising third-year pro Devery Henderson for a 76-yard touchdown in the Saints’ 31-13 victory over Atlanta.

“Drew Brees is getting the ball to everybody. You can’t just concentrate on one guy over there,” said San Francisco cornerback Walt Harris, who leads the NFL with six interceptions and has forced three fumbles. “We’ve had tests throughout the year. It’s just going to be another high-caliber quarterback that we have to deal with.”

Harris has led a defense that has been big on takeaways lately, intercepting six passes and recovering seven forced fumbles in its last four games. That should be worrisome to the Saints, who had a clean game last week, but remain near the bottom of the NFL with a turnover margin of minus-9. “It’s a defense that’s kind of night-and-day compared to the beginning of the season,” Brees said. “They’re playing solid football. They’re playing with a lot of confidence, and we’re going to have to combat that with execution and playing with our own confidence.”

A part of both teams’ sudden success has been the performance of young players who used to be high school teammates in San Diego: San Francisco quarterback Alex Smith and Saints running back Reggie Bush.

“Weird, very weird. I never would have imagined back in high school that this ever would have come,” Smith said. “But it’s exciting, you know? It will be exciting to get to play against him, to see him, to see what he’s doing out there.”

While not performing anywhere close to Brees’ level, Smith is much improved over his rookie season, when he had one TD pass and 11 interceptions. With the help of versatile running back Frank Gore (1,177 yards rushing, 318 yards receiving), Smith has been under less pressure and has responded with a 60.9 completion percentage and 11 touchdowns.

And San Francisco has been winning enough lately to have the Saints talking about the 49ers like they’re a potential force in the NFL again.

“We know that coach Nolan is telling them this is their last chance to have a shot at the playoffs. We know that, and that’s the way we’re preparing,” Horn said. “We’re not going to take them lightly. We need everything to click at one time, the fans, the play calling, the defense, everything, because we know the 49ers can be dangerous. Very dangerous.”