49ers at Saints -- Week 12

Where: Mercedes-Benz Superdome, New Orleans, La. (Indoors, artificial turf)

When: Sunday, 4:25 pm. (Fox)

Spread: 49ers by 1

Records: Saints (5-5, 1-2 NFC South); 49ers (7-2-1, 2-0-1 NFC West)

Past results: Two most recent meetings -- Jan. 14, 2012: 49ers 36, Saints 32 at Candlestick Park in the divisional round of the NFC playoffs; Sept. 20, 2010 -- Saints 25, 49ers 22 at Candlestick Park. Series record: 49ers lead 46-24-2, counting the playoff game. The 49ers are 19-11 at the Superdome but have lost four in a row there, last winning on Jan. 6, 2002.

What matters: For the Saints, it's getting above .500 while keeping that second-half surge going. Since the NFL went to eight divisions in 2002, only one of 38 teams that started 0-4 has rebounded to get above .500 at any point of the season. None of them have finished better than 8-8. The Saints can improve to 6-5 with a win, and this game is monumentally important as they try to buck history and become the first 0-4 team to make the playoffs since San Diego in 1992. San Francisco has been erratic -- dominant defensively in its seven wins and lousy across the board in its two losses and a tie -- getting hammered 26-3 at home by the New York Giants, falling to Minnesota 24-13 and giving up 458 yards to struggling St. Louis. The Saints barely beat Atlanta and Tampa Bay, and their other victims in their 5-1 stretch (San Diego, Philadelphia, Oakland) have combined to lose 15 of their last 18 games, with the wins against Kansas City (twice) and Jacksonville. Sunday will be the litmus test for the Saints’ true form. Win, and they are a serious playoff contender. Lose, and their recent run will be put in perspective.

Who matters: Drew Brees -- Although they ran the ball well the past three weeks, the Saints did not face a defense like San Francisco’s. The 49ers allow 3.7 yards per carry, the third lowest total in the NFL. The Saints gained well under 100 yards on the ground against the No. 1 and No. 2 rush defenses (Tampa Bay, Denver) and rushed for 37 yards vs. the 49ers in the 2011 playoffs. Brees need to be at his best, sliding away from the pass rush, finding the open receiver and beating the 49ers over the top. The formula worked in the playoffs last year. The Saints lost, but their 32 points were the most the 49ers have given up in the Jim Harbaugh era. … LBs Curtis Lofton and Jonathan Vilma -- San Francisco QB Colin Kaepernick excelled against Chicago on Monday night, but this will be his first road start. If Lofton and Vilma corral RB Frank Gore, Kaepernick will be pressured to produce. The LB duo is meshing well together. Although the stats don’t show it, New Orleans is much better vs. the run than earlier in the year.

Key matchup: The Saints RT vs. 49ers OLB Aldon Smith. This has the potential to be an epic mismatch. Smith had 5 ½ sacks against Chicago last Monday, giving him 29 in his first 26 games (an NFL record). He frequently lines up on the left side of the 49ers line in their 3-4. The Saints will counter either with Zach Strief, who has missed the last two games with a groin injury and has been limited in practice this week, or third-string undrafted rookie Bryce Harris, who was forced into action last Sunday against Oakland when Strief’s backup, Charles Brown, left with a knee injury. This one will be a headache for offensive coordinator Pete Carmichael and OL coach Aaron Kromer. The Saints can help out with their tight ends, but Jimmy Graham does not block much, leaving David Thomas as the only option. Coming up with an answer for Smith could be the difference between winning and losing.

Injuries of note: The Saints will be without nickel back Corey White (left knee), but the key is the health of Strief (questionable) and RB Darren Sproles (broken left hand), who practiced all week.

Inside stuff: The obvious angles for this game are overdone. The Saints looking for revenge after last year’s heartbreaking divisional playoff loss? It’s a different season, and winning would be huge regardless of the recent history. The 49ers taking out their anger about the “kill the head” locker room speech that former Saints defensive coordinator Gregg Williams gave before their playoff game last year, the one that ultimately busted BountyGate wide open? Williams is no longer around and coaches say over-the-top stuff all the time. By the opening kickoff, those issues will be window dressing.

Connections: 49ers center Jonathan Goodwin played with the Saints from 2006-10. … Saints LB Jonathan Vilma and 49ers RB Frank Gore were teammates in high school and at the University of Miami. … 49ers defensive coordinator Vic Fangio was the Saints' defensive coordinator from 1986-94.

Stats you should know: The Saints have given up more than 400 yards in their first 10 games, extending an NFL record. … The 49ers have held five opponents to 7 points or fewer. The Bears are the only other NFL team to do that more than twice (3). … Sproles had a playoff-record 15 catches for 119 yards against San Francisco last year.

Record watch: Marques Colston remains tied with Deuce McAllister for the Saints’ all-time TD record with 55.

Bulletin board quote: "It doesn’t really matter who plays. One runs more than the other one, but the offense doesn’t change no matter whom the quarterback is. Our key to victory is really stopping the run." -- Saints DE Will Smith on the 49ers QB situation.

Looking ahead: The Saints travel to Atlanta for a Thursday night game. It’s tough to have a short week after playing the physical 49ers. New Orleans then plays at the New York Giants on Dec. 9. This is one rough three-week stretch.

Prediction: Saints 24, 49ers 20

Follow Saints reporter Guerry Smith on Twitter @CBSSaints.