EAST RUTHERFORD, N.J. -- Carolina Panthers safety Roman Harper looked like he was getting dressed for a funeral as he put on a dark suit and black tie following Sunday's 38-35 victory over the New York Giants.

His demeanor certainly was somber.

Others around him were just as gloomy. Nobody was smiling, dancing, playing loud music ... or any of the things they have done in recent weeks.

This didn't feel like a winning locker room, much less one of a team that improved to 14-0 with a last-second field goal by Graham Gano.

"This is the most disappointed 14-0 locker room I've ever seen in my life, and rightfully so," Harper said.

That's because the Panthers allowed the Giants to erase a 35-7 deficit over the final quarter and two minutes. That's also because they got so wrapped up in the feud between cornerback Josh Norman and wide receiver Odell Beckham Jr. that they lost their composure.

Harper and others seemingly understood the Panthers can't allow that to happen in their pursuit of perfection, particularly in the playoffs, or else their goal of winning a Super Bowl could come to a crashing halt.

Then the mood really would resemble that of a funeral.

Coach Ron Rivera was just as disappointed as Harper.

"We had an opportunity to close a team out and we didn't do it," he said. "Why? Because we didn't keep our focus and maintain our composure out there.

"Bottom line is you've got to stay focused when you play this football game. If you don't, that's what's going to happen."

Rivera has talked often about wake-up calls that will help the Panthers refocus the closer they get to 16-0. They got one three weeks ago at New Orleans, where quarterback Cam Newton had to throw a touchdown pass to Jerricho Cotchery with 1:05 remaining for a 41-38 victory.

They answered the following week with a 38-0 victory against Atlanta that was their most complete game of the year.

Sunday's game at MetLife Stadium represented another wake-up call. It was a reminder that when you get away from your identity, bad things can happen.

The Panthers got away from their identity in the third quarter when the focus was on Beckham and Norman and who would get more personal fouls. Beckham finished with three and Norman two.

"We got caught up in all the talking and jawing and away from things we pride ourselves on, which is being a smart team," Harper said. "We did some things that were uncharacteristic of ourselves, and we're going to get better from this."

Norman in particular must get better from this. Because he's so brash and confident, Norman gets some opponents to go to that dark place he talks about going to.

Receivers are going to try to get into Norman's head even more moving forward because of what happened on Sunday.

"Josh has got to learn to play through those things," Rivera said.

It wasn't just the defense that got caught up in the feud. Newton pulled Norman aside in the second half to talk to him.

Newton called it a "personal talk." That he had to use energy on that instead of the offense showed the shift in focus.

"It shouldn't have been a thriller, I can tell you that," Newton said of the game.

In the same breath, Newton said it was "great for us to be in a game like this." He called it a minidose of what the Panthers could face in the playoffs.

In other words, a wake-up call.

That's why the locker room resembled more of what you would expect from the losing team.

Newton finally cracked a smile when told what Harper said about being a "disappointed 14-0 team." He reminded those around him that Harper was a member of the 2009 New Orleans Saints that lost to Dallas after a 13-0 start.

Newton admitted "it was kind of a weird feeling" in the locker room but that ultimately Carolina had something to celebrate because it won.

The Panthers won in large part because Newton continued to play at an MVP level by registering five touchdown passes for the third time in five games. Newton also rushed for 100 yards, including 10 on the final drive to put Gano in position to kick the winner.

Based on history, getting to 14-0 is a good thing. The other three teams in NFL history to reach that mark made it to the Super Bowl, although only the 1972 Miami Dolphins won it all.

Even Harper couldn't deny the positives through his sullen look.

"We're good," he said. "We're going to be better. This is the most disappointing 14-0 team I've ever seen in my life, and that's a great thing because we hold ourselves to such a high standard."