TAMPA, Fla. -- Only a few days ago, Carolina Panthers quarterback Cam Newton said he "straight up" was playing the best football of his career.

Four interceptions and a badly overthrown pass on what could have been the tying touchdown with just over two minutes left in Sunday's 24-17 loss to the Tampa Bay Buccaneers and the Panthers don't even have that going for them.

The wheels haven't just come off. They've flown off.

Carolina (6-6) has gone from one of the best teams in the NFC and on a collision course with the New Orleans Saints for the division title to a team in disarray with four straight losses.

The signs of a team in a free fall are everywhere.

Coach Ron Rivera on Sunday got more involved in the defensive playcalling in an attempt to turn around a unit that has underachieved for much of the season. That doesn't bode well for first-year defensive coordinator Eric Washington.

Pro Bowl tight end Greg Olsen appears out for the remainder of the season after rupturing the plantar fascia in the same right foot that sidelined him for nine games last season when he broke it and for three games earlier this season.

It's gotten so bad that questions about job security exploded into Rivera's postgame news conference because CBS Sports, citing multiple league sources, said new team owner David Tepper is mulling major changes if the team doesn't turn its performance around.

"At the end of the day, unless Mr. Tepper says it, I'm not going to address it. OK?" Rivera said. "We can forget about asking me those questions, please."

When asked a few minutes later if he was concerned about his job security, Rivera's voice grew louder.

"I am not going to address that question," he said. "Do not ask that question again, please."

There are lot of questions about why the Panthers have fallen so hard so fast. The issue is nobody has hard answers.

"If I had the answer, we would have fixed it," said center Ryan Kalil, who before the season announced this was his last campaign. "I don't know ... It's not a lack of caring. It's not guys quitting. We don't have a problem playing hard.

"But there's a difference between playing hard and smart, disciplined football. We're just not doing it, especially in critical situations."

Newton had been able to keep the Panthers in most games because, for the most part, he avoided the critical mistakes. It all unraveled on Sunday when the 2015 NFL MVP started throwing picks that kept Carolina from overcoming an early 10-0 deficit.

"I take this one personal because I know I keep running off this field in embarrassment, really, knowing that you're leaving because of your mistakes," said Newton, who had only seven interceptions in the first 11 games and hadn't thrown four in a game since his rookie season against the Detroit Lions. "We just have to find ways to get back in the win column, and I feel like we're on a brink."

This season is on the brink of disaster if it doesn't already qualify for that.

But no one on Sunday was blaming Rivera, the NFL Coach of the Year in 2013 and 2015, or the coaching staff.

"He's won a lot of games around here, had a lot of success around here," Olsen said of Rivera, who is four regular-season wins away from passing John Fox (73) as Carolina's winningest coach. "That kind of stands on its own.

"It's always easy to feel certain ways after bad losses, tough games. These aren't the times to talk about those sort of things. We're on the record over the last eight years what we feel about Ron. A lot of what's gone on this year is a player-driven, performance-driven problem."

This loss was driven by the poor performance of Newton, who came into the contest with a personal-best six straight games with a passer rating of 100 or more.

This loss was driven by the offensive line's inability to give Newton more time; he was sacked four times and hit nine times.

This loss was driven by the defense making critical mistakes, such as two pass interference penalties on Tampa Bay's game-winning touchdown drive.

While the second call was questionable, something Rivera chose not to address, those are the things that consistently have happened during this skid.

"At this level, players, including myself, there's a lot we can do to change the results on the field," Olsen said. "That's our big concern."

Kalil agreed, saying Rivera is "one of the all-time best."

Five weeks ago, the Panthers appeared one of the best squads not only in the NFC, but perhaps the NFL.

Now they have to deal with finding answers over the final four games -- starting with a trip to the Cleveland Browns -- and the outside noise surrounding potential changes to the staff.

"As far as I'm concerned, unless Mr. Tepper puts his name on it, everybody just needs to calm down and let what's really being said and let the truth come out," Rivera said. "If anybody has a question, they should ask Mr. Tepper."