Updated

The Arizona Cardinals were supposed to backslide with the loss of starting quarterback Carson Palmer.

Quite the opposite has happened.

For the second week in a row, backup Drew Stanton directed the Cardinals to victory, this time a 24-13 triumph over the San Francisco 49ers. The win on Sunday left Arizona 3-0 and alone atop the NFC West heading into next week's bye.

"This was a huge step to a great season ahead of us," Arizona cornerback Patrick Peterson said.

The 49ers, meanwhile, fell flat in the second half for the second week in a row. San Francisco was outscored 17-0 in the second half. For the season, opponents have outscored the 49ers 52-3 in the final two quarters. San Francisco could take heart in the fact that they started 1-2 last year, then went 10-3 the rest of the way.

"We have 13 more games left," San Francisco fullback Bruce Miller said. "Take it one game at a time, and we'll get back in the mix."

Stanton threw a pair of third-quarter touchdown passes to rookie John Brown and the Cardinals' defense stiffened in the second half. The 49ers helped out with six of their nine penalties. Overall, the 49ers were penalized 107 yards.

The Cardinals snapped a four-game losing streak against San Francisco, beating the 49ers for only the second time in 11 tries.

"We talk about making a statement in our divisional games at home," Arizona coach Bruce Arians said, "making this a tough place to come to, and that was a big victory for us."

Dating to last year, the Cardinals have won 10 of 12 games.

Here are things to note from the Arizona victory over San Francisco.

COMEBACK CARDINALS: The Cardinals have come back from a second-half deficit in all three of their victories. They were down 14-6 at the break on Sunday.

"Guys listening at halftime," Arians explained, "listening to the adjustments and coming out positive. We talked about the first five minutes of the third quarter being huge ... We were able to get the touchdown. From there it snowballed. The crowd was fantastic, and I can't say enough about how they helped in the second half of these games."

49ER PENALTIES: For the second straight week, penalties plagued San Francisco. They drew nine for 107 yards, including 30 yards worth in Arizona's 66-yard drive for the go-ahead touchdown.

Wide receiver Anquan Boldin blasted the officiating.

"Every week is the same thing," he said. "You send the tape in and the NFL reports back that we made a mistake, but at the same time ... (it) is costing us games. At some point they need to be held accountable."

The crucial penalties on that Arizona scoring drive were an unnecessary roughness call on linebacker Dan Skuta on Stanton, followed immediately by a roughing-the-passer call against linebacker Patrick Willis.

Skuta said he talked to Stanton after the game and the Arizona quarterback said "I knew it was a bad call."

BROWN'S MOM: Brown is extremely close to his mother, Casandra. Palmer has joked that he calls her a thousand times a day.

And for the first time, she was there to watch him play.

"It's a good feeling," he said. "I just did what I have to do to make her proud."

The speedy wide receiver from little Pittsburg State caught TD passes of 24 and 21 yards.

Brown said she had seen him play once in college.

KAEPERNICK'S GAME: The Cardinals couldn't stop the athletic San Francisco quarterback early in the game. He completed his first nine passes, seven of them on the opening drive, when he also ran for 37 yards. Kaepernick finished 29 of 37 for 245 yards and a TD along with a team-high 54 yards rushing.

"Man, Kaepernick's a beast," Arizona defensive end Calais Campbell said.

San Francisco came out with no-huddle and multiple receiver sets that seemed to surprise the Cardinals.

"We hadn't shown that before," Kaepernick said. "It was something new. In the second half we ran it here and there."

CROMARTIE'S KNEE: Antonio Cromartie, a big addition to Arizona's secondary this season, left in the first half with an injured left knee.

It's the same knee he injured in 2005, costing him an entire season at Florida State. But Cromartie downplayed its significance.

"Thank you guys for your prayers," he said in a tweet. "But I'm fine and will (be) ready for the week 5 matchup vs the Broncos."

NO DISTRACON: There was almost no mention of the week's big news: the arrest of Arizona backup running back Jonathan Dwyer on domestic violence charges. He has been placed on a non-football/illness list, which means he's paid until the legal outcome is known but he won't play this season.

"We had a bunch of things that people from the outside looking in would see as distractions," said Arizona safety Tony Jefferson, who had 10 tackles and a sack, "but we held our own."

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