The Celtics’ predicament isn’t all on Joe Mazzulla. The players need to rediscover their pride to avoid an embarrassing sweep.

The Celtics' two All-NBA stars, Jaylen Brown and Jayson Tatum, must rise to the occasion on Tuesday.Adam Glanzman/Getty

MIAMI — Monday was a beautiful day in the Brickell area of Miami, a day for the Celtics to refresh and reflect after their humiliating performance Sunday against the Miami Heat, and also a day for more concrete reasons why they are trailing this series 3-0.

This team has descended over the past few months, plummeting from a NBA championship favorite to an unstable bunch who cracked under the pressure of the Heat — no pun intended— in the past three games.

The Celtics have not improved since the All-Star Break. They have been relying solely on talent, meaning their once-daunting defense has dissipated into a bunch of unconnected individuals who relent at the first sign of pushback.

Privately, the Celtics have been stunned the Heat are playing so well. They have flipped the switch and the Celtics seem completely demoralized when they make the proper defensive play and Gabe Vincent, Max Strus, or Caleb Martin still hits the shot.

So now, a coach potentially fighting for his job, his livelihood, and his reputation has to encourage his players to drum up enough motivation and pride to avoid a sweep. But pride is a personal trait and it’s not something Mazzulla can coach into Jayson Tatum or Jaylen Brown in 48 hours.

Those two All-NBA players need to digest all the criticism they’re receiving and turn that into fuel for their best games of the series, or at least the desire to respond to Miami’s increased trash talking and showboating. A developing element to this series is the Heat’s voracious desire to humiliate the Celtics and the Celtics accepting such fate without much resistance.

The Celtics have never been considered a tough team, but they were resilient once upon a time, and comments from players continue to be, perhaps, an unintended indictment on Mazzulla’s leadership. Malcolm Brogdon, whose brutal honesty this season has been refreshing and his perspective fresh since he was not a member of last year’s team, admitted the Celtics have lost their culture over the past few months.

When he took over for Ime Udoka, Mazzulla immediately stressed offensive improvement, more 3-pointers, and more floor spacing. Now the Celtics have become offensively predictable, a team that is too 3-point reliant and just ignores midrange shots and easier 2-point scoring opportunities. And a team that prided itself on defense but has slipped considerably partly because of its emphasis on offense and partly because it allows offensive shortcomings to impact its desire to defend.

“I think in the Atlanta series, the Philly series, we got away with things that now are biting us,” Brogdon said. “So that’s definitely troubling. I think it’s mainly on the defensive end. We haven’t been consistently great all year long. That was the team’s identity last year and that slipped away from us. We’ve had spurts where we’ve been great defensively, but not consistently. We’ve struggled in every series we’ve played.

“Now we’re playing a team that’s playing as if they’re the best team in the league and they’re just incredibly disciplined, incredibly consistent. We’re a team that all year long has relied on making shots and when we don’t make shots, our defense wanes. It slips. It’s something we’ve tried to work on.”

Tatum and the Celtics were frustrated by the Game 3 loss in Miami,Jim Davis/Globe Staff

Frustration has turned into questions of commitment and belief. The Heat are shooting 51.9 percent from the field and 47.8 percent from the 3-point line in the series. Vincent, Robinson, and Martin have combined for 28 3-pointers. The Celtics have made just 31 as a team. Those are discouraging numbers. Martin hit 84 3-pointers in 71 regular season games and yet had 10 in three games.

The more they pound the Celtics into oblivion, the more brash the Heat get. Jimmy Butler mimicked Al Horford’s timeout pose after Miami took a 23-point lead, with five Celtics walking past him but Horford the only one bold enough to utter a word in response.

The Heat are visibly trying to embarrass the Celtics and the Celtics are losing their pride and dignity in the process. Something has to change for Game 4.

“It’s a sense of understanding that it’s pride for everybody; it’s a team pride,” Mazzulla said. “It’s a pride that we’ve had throughout the year and we have to maintain. Yes, there is [pride] on a personal level, but we’re in this together. And we have to have that pride together.

“Coming into this series, it’s a test of discipline, a test of mentality and all of their guys are making shots right now. We have to be clearly defined with which ones we’re living with and which ones we’re taking away.”

It’s up to the players to determine their fate, regardless of Mazzulla’s influence. The players have to execute, close out on shooters, get back on defense, stop complaining about calls, and create good fortune instead of hoping for it.

In other words, the Celtics have to play like a team that knows it’s the best on the floor even if they don’t fully believe it. If they don’t believe they can turn this into a competitive series, what’s the use of even taking the floor Tuesday?

“There’s a lot of pride,” Brogdon said. “To wear the Celtics jersey. This is a very good team. We had a great regular season. We’ve shown moments of greatness. We just have to put it together. Losing separates people and divides people and this has been a frustrating series for everybody. We just have to win a game.”

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