GLENDALE, Ariz. — A day that started with the home fans booing Cardinals quarterback Carson Palmer ended with a more festive atmosphere inside University of Phoenix Stadium – and a quiet, somber mood in the Panthers locker room.

Quarterback Cam Newton was sacked seven times and lost four turnovers, including a costly fourth-quarter interception, as the Panthers fell 22-6 in a mistake-filled game of penalties, dropped passes and Newton miscues.

“When their fans are booing them in the first quarter that’s a beautiful thing,” left tackle Jordan Gross said. “But then when they’re doing the wave in the fourth quarter, obviously things didn’t go well for us.”

Another sign things didn’t go well for the Panthers: When Newton has as many or more tackles – he chased down two Cardinals after turnovers – than four defensive starters.

Any positive energy the Panthers (1-3) gained following their 38-0 shutout of the Giants two weeks ago was lost in a sloppy offensive effort. It was the first time the Panthers failed to score a touchdown since a 30-3 loss to Tennessee on Nov. 13, 2011.

“We had an opportunity to be 2-2, keep a win streak going, go on the road with another winnable game (against Minnesota),” said free safety Mike Mitchell, who had one of the Panthers’ three interceptions against Palmer. “We were in second place. We had a lot to gain by winning this game.

“These are swing games. You win this one, now you’ve got two in a row, it could turn into five, six, seven games.

“Now you win one, you lose, you win, you lose – you don’t want that. That’s how you end up 8-8.”

It’s also how you end up with a fired coach.

According to an NFL.com report Sunday, the Panthers have begun doing background checks on possible candidates to replace Ron Rivera if they decide to make a coaching change.

But this loss wasn’t on Rivera. The Panthers self-destructed during three trips inside the red zone, with dropped passes by their top two receivers in the first half and Newton’s fourth-quarter interception.

Smith’s drop came in the end zone on the Panthers’ opening series, after rookie safety Robert Lester picked off Palmer on the Cardinals’ first possession. Smith was open on a slant route, but had the ball go through his hands.

It was one of two drops for the normally sure-handed Smith, who told reporters after the game to blame the loss on him.

“That’s not Smitty. I know that. We all know that. But it happens,” Newton said. “We still have to come back and hold ourselves accountable and just say, ‘Look, no matter what happens, I’m still going to be consistent enough to lead this team.’”

Three series later, Brandon LaFell dropped Newton’s short pass on fourth-and-1 from the Cardinals’ 15. Rivera said the drops hurt the Panthers’ momentum.

“Steve’s going to make plays for us, he’s going to make a lot of plays. And unfortunately he dropped one that he had an opportunity to catch. Same thing with Brandon LaFell. ... These are guys that can’t do that in certain situations,” Rivera said.

“I think sometimes when you don’t score touchdowns, it takes the wind out of your sails when you’ve got to settle for a field goal.”

Despite outgaining Arizona 259 to 118 in total yardage in the first half, the Panthers led only 6-3 at the halftime. They lost the lead when the Cardinals drove 85 yards for a touchdown on their first second-half possession.

Arizona (2-2) tacked on a safety to go up 12-6 in the third quarter when the Panthers had a communication breakdown along their offensive line.

A play after left guard Amini Silatolu left with a right knee injury, defensive end Calais Campbell beat center Ryan Kalil to drop Newton in the end zone. Campbell wasn’t even supposed to be in for the play, but cornerback Patrick Peterson prodded him during the injury timeout.

“I was sitting on the sideline for a second and a player got hurt, so there was a lot of time left for me to get in there,” Campbell said. “Patrick Peterson was like, ‘Come on, we need you. Come make a play.’”

Kalil was expecting help from Travelle Wharton, who replaced Silatolu. But Kalil said it was his fault for not getting the protection relayed to Wharton.

The safety was one of seven sacks of Newton, matching the sacks Denver had against Newton in a Broncos’ victory last season.

Meanwhile, the Panthers sacked Palmer only twice – two weeks after tying a franchise record with seven against the Giants’ Eli Manning.

“He was getting the ball out. They had a sufficient gameplan,” defensive end Greg Hardy said. “Carson gets the ball out, they push us upfield. I feel like we had a good pass rush, we hit him enough times. It’s just kudos to those guys.”

The Panthers had nine penalties after being flagged 11 times the first three games.

Newton won the BCS title game here with Auburn, and set a rookie passing record with 422 yards in the same stadium two years ago in his NFL debut against the Cardinals.

Newton threw for 308 yards Sunday. But he lost a fumble and threw three interceptions, including one in the red zone when the Panthers were threatening to take the lead.

Trailing 12-6 and facing third-and-3 from the Cardinals’ 11 on the first play of the fourth quarter, Newton looked to Smith on a slant route, despite blanket coverage by Peterson. Linebacker Daryl Washington stepped in front of the throw for the interception, returning it close to midfield before Newton forced him out of bounds.

It all added up to another early season loss for a team that was plagued by slow starts in each of Rivera’s first two seasons.

“Unfortunately, we’ve been here before. The last two years were similar to this and we ended up winning games at the end. So I don’t worry about anybody quitting,” Gross said. “But we’ve got to figure out how to win games in October. Not winning now and then winning in December doesn’t do you much good.”

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