NEW ORLEANS – The 49ers entered Sunday's game with their collective eye on lightning-quick Reggie Bush but ended up getting blindsided by Deuce McAllister.

McAllister, who had just two total carries entering the game, got the ball 20 times against the 49ers and ran for 73 yards and a touchdown. The 232-pound running back, being eased back into the Saints' offense after tearing an ACL last season, seemed to be the perfect antidote for the nickel defense the 49ers hoped would slow down quarterback Drew Brees and the Saints' prolific passing attack.

"We just felt by the nature of the game that this week we had a chance to run the ball more," New Orleans coach Sean Payton said. "We saw a lot of nickel defense and we felt like we could take advantage of that, so we kind of mixed up our personnel and it worked out pretty well."

It was a cat-and-mouse game won by Payton, Brees and the Saints.

In one second-quarter sequence, McAllister ran three consecutive times, picking up 10, six and six yards. The 49ers adjusted by moving out of their nickel package and back to their base package.

Almost immediately, Brees hit receiver Lance Moore, who had badly beaten safety Dashon Goldson, on a 33-yard touchdown.

Afterward, linebacker Patrick Willis said the 49ers expected to see plenty of Bush, who scored twice last week against Denver and touched the ball 33 times. Against the 49ers, however, Bush touched the ball only 15 times and had just seven receiving yards.

Coach Mike Nolan, meanwhile, insisted it wasn't McAllister but rather the big pass plays that doomed his defense.

"We anticipated (McAllister) to play, yes," Nolan said. " … Yes, you don't want to have a guy get first downs, but that's going to happen time to time. But the big pass plays that went for first downs or got close for first downs – those things were the game-changing plays."

Sack party – For the second time this season, the 49ers allowed six sacks. The two biggest culprits appeared to be quarterback J.T. O'Sullivan, who held the ball too long early in the game, and right tackle Barry Sims, who had a difficult time handling New Orleans defensive end Charles Grant late in the game.

Grant finished with two sacks, and on one fourth-quarter sequence hit O'Sullivan as he was throwing the ball on two consecutive plays.

"We just didn't play well as a unit," said Sims, who is filling in for an injured Jonas Jennings. "Up front, we all had our breakdowns. When your (quarterback) is taking hits constantly, it tends to get you out of rhythm."

Et cetera – The Saints' defensive backs were particularly effective at jumping the slant routes the 49ers had relied on in previous games. Said receiver Bryant Johnson, who was held without a catch: "They kind of cheated a little bit. We started to make adjustments, but we were still behind the gun a little."

• Safety Michael Lewis was questionable for the game with an elbow injury but ended up leading the team with 11 tackles. He also forced a fumble at the 49ers' goal line in the fourth quarter that the 49ers converted into a 97-yard touchdown drive.

• Mark Roman was one of several 49ers safeties victimized for a long touchdown pass. Roman, who had 150 friends and family in town from his home of New Iberia, La., left the locker room without talking to reporters.

• Linebacker Manny Lawson didn't start the game because the 49ers mostly played in their nickel defense. However, he strained his left hamstring while on special-teams coverage and did not return.

Read Matthew Barrows' 49ers blog at www.sacbee.com/ninersblog.