Coming close to a championship doesn’t cut it in Boston. This summer, the Celtics put their money where their mouth is.

Less than a month removed from a heartbreaking Game 7 loss to the Heat, and a year after coming two wins short in the NBA Finals, they shook everything up to their core. Literally. Marcus Smart – the franchise’s cornerstone, heartbeat and backbone – was shockingly traded as they acquired Kristaps Porzingis.

“Sometimes really, really hard decisions have to be made,” Brad Stevens said shortly after.

If it wasn’t already clear the Celtics weren’t messing around, they doubled down on the eve of training camp. In the wake of Milwaukee’s acquisition of Damian Lillard, the C’s didn’t hesitate to jump ahead of other contenders to trade for Jrue Holiday.

The message was simple: It’s time to win. Now.

“Is there pressure?” Jayson Tatum said. “Yeah, we have a really good team. We have really good players. People expect us to get to the championship and win, and when we don’t, we didn’t necessarily meet expectations.”

There are no excuses this year.

The Celtics have the most talented roster in the league, led by All-NBA players Jayson Tatum and Jaylen Brown. They now have a proven champion in their locker room in Holiday. The franchise’s ownership headed by Wyc Grousbeck and Steve Pagliuca gave Stevens the nod to blow through the salary cap’s second apron, putting all their chips on the table this season to win their first championship since 2008.

For the Celtics, it’s championship or bust.

Five keys for the Celtics as they begin their quest for Banner No. 18 with tonight’s season opener against the Knicks:

1. Health

It seems obvious, but yet for these uber-talented Celtics, staying healthy might be the most important key. If they do, there’s no reason they won’t be celebrating next June.

Of course, that’s easier said than done. And it requires some luck. The Celtics weren’t as fortunate last season, when they lost Robert Williams for the first two months of the season – though they overcame that – before staying relatively healthy until the Eastern Conference Finals. That’s when, at the worst possible time, Malcolm Brogdon suffered an injury that kept him out of most of the final round before Tatum’s brutal ankle injury on the first play of Game 7. If those injuries don’t happen, the end of last season might have been a different story.

Celtics takeaways: Kristaps Porzingis shines in debut as C’s win preseason opener

All eyes this season center on Porzingis. The 7-foot-3 center’s injury history is no secret. Just this summer, he suffered plantar fasciitis in his right foot that forced him out of the FIBA World Cup. He returned to Celtics training camp fully healthy and looked terrific in the preseason with no restrictions.

It was no coincidence that Porzingis had a career season last year in Washington while having one of the healthiest seasons of his career, and the Celtics are hoping he will build on that as he enters his prime. He’s an elite three-level scorer who’s almost impossible to stop with his combination of size and skill, and his presence is expected to make the Celtics’ offense unstoppable. But there is some uncertainty with Porzingis, who has only played in 10 playoff games in his career. Can he hold up for a full season, and how will he endure a grueling playoff run while matching up against the likes of Bam Adebayo, Giannis Antetekounmpo and Joel Embiid?

After the departure of Robert Williams, the frontcourt depth is thin if Porzingis or 37-year-old Al Horford go down at any point. That’s a risk the Celtics are willing to take, and it could certainly impact the outcome of their season.

2. Defensive consistency

The Celtics were certainly no slouches on defense last season as they finished second in the league in defensive rating in the regular season. But they could never count on it like they did during their NBA Finals run in 2022. It let them down during the Eastern Conference Finals, when inconsistency on that end put them in a 3-0 series hole they ultimately couldn’t recover from.

While they traded their defensive quarterback in Smart, the Celtics made defense a priority this summer.

It started with Brown, who went out of his way during his supermax extension press conference to say he wanted to make sure the Celtics didn’t rest defensively for the upcoming season. That message continued through training camp and the preseason.

“I think that we’re going to go into the year stronger defensively,” Brown said. “I think we gotta continue to emphasize that throughout the year and can’t let it dip or wane. I want to be one of the guys that makes that an emphasis for us. Obviously we have some All-NBA defenders, Jrue and (Derrick) White. We gotta come in and really have an impact for 82 games on the defensive end of the ball.”

Boston Celtics center Al Horford, right, and New York Knicks guard Donte DiVincenzo battle for a loose ball as the Celtics hosted the preseason game Tuesday. (Staff Photo/Stuart Cahill/Boston Herald)

The acquisition of Holiday was essential, giving the Celtics the grit and toughness they lost with Smart. Arguably the best defensive guard in the NBA, Holiday’s ball pressure and defensive acumen is a game-changer for the Celtics on that end of the floor. He’ll pair up with another all-league defender in White to form the best defensive backcourt in the NBA. Tatum and Brown seem motivated to show what they can do defensively, Porzingis and Horford provide great rim protection and the Celtics boast several versatile defenders on their bench. The personnel for a great defense are there.

The coaching is there, too. Celtics coach Joe Mazzulla admitted at the start of training camp that he didn’t do enough last season to demand consistent defensive performances. That messaging has changed this season. Mazzulla has emphasized it in different ways. Last season, the C’s ranked at the bottom of the league in forcing turnovers, and Mazzulla identified that as a focus this season as he tries to remove the variance of bad shooting nights by creating more possessions.

“There was a lot of times last year where we were a great defensive team, and there were times where we didn’t make that our foundation,” Mazzulla said. “So at the end of the day, you just have to compromise. Defense is what gets you in the door, defense is the admission ticket, but it’s toughness, it’s mindset, it’s the ability to just be physical on both ends of the floor. So you just have to do it, like you don’t have a choice.”

3. Next step for Tatum, Brown

The lasting memories of last spring weren’t fond for Tatum and Brown. Tatum’s last meaningful minutes of the season were spent trying to overcome that ankle injury, and he never did. With Tatum hobbled, Brown tried to do more than he could and he committed a career-high eight turnovers in the Game 7 loss.

The two Celtics stars, fair or not, have received most of the blame when things go wrong. But now, after years of experience, there are no excuses left for them. It’s time for them to deliver.

The trade of Smart was perceived by some to allow Tatum, entering his seventh year, and Brown, entering his eighth, to grow as the leaders of this team, and both have acknowledged that their voices will get louder and that they need to do more in the absence of their former point guard. This is undoubtedly their team now. Both have another level to reach, most importantly in the final stages of the playoffs, where both of them have come up short the last couple of seasons.

Boston Celtics guard Jaylen Brown (7) greets Boston Celtics forward Jayson Tatum (0) prior to the game as the Celtics take on the Knicks at the Garden on October 17, BOSTON, MA. (Staff Photo By Stuart Cahill/Boston Herald)

Brown, after signing a record contract extension this summer, knows there’s an even bigger responsibility to deliver now.

“I would be lying if I said I wasn’t motivated,” Brown said. “I’m extremely motivated. I’m the type of guy that always finds a chip on my shoulder … not being able to get to the ultimate goal so far in my career is something that gives you extra motivation. So I’m excited about the year. I’m excited about the journey and I’m ready to go.”

4. Mazzulla a year wiser

Mazzulla admitted that last training camp was a blur. Suddenly thrust into the job after Ime Udoka’s suspension, the rookie head coach had no time to think. He overcame growing pains for most of the regular season but made some costly mistakes in the playoffs. It didn’t help that he lost his top assistant mid-season, either. There was a lot to learn.

But entering this season, Mazzulla is set up for success. He had the benefit of a full offseason to prepare, and he’s now surrounded by plenty of experience around him, including new assistants Sam Cassell and Charles Lee. The Celtics even added Jeff Van Gundy to the mix as a senior consultant.

Jayson Tatum praises Celtics’ culture change under Joe Mazzulla: ‘We’ve all bought in’

Last season, Mazzulla could be excused for some of the mistakes he made. But not so much anymore. To his credit, he’s taken full accountability and ownership. His first season provided plenty of lessons to apply this year, and he’s already started.

“I’ve seen the growth,” Tatum said. “Not that he didn’t do a great job last year, but he’s just had more time to prepare. He was able to get a staff that he felt like supported him the best way. And he’s helped change the culture a little bit in a lot of ways honestly. I feel like he’s had his imprint on how he wants things to be, how he wants to practice, how he wants the environment, the vibe. And we’ve all bought in.”

5. Sacrifice

One of the buzzwords of camp has been sacrifice, and it’s been shouted from the top.

Beyond health, a team this star-driven could realistically only be derailed from within. There’s a ton of talent, and a team this loaded obviously doesn’t always work like it’s supposed to, especially in the recent history of the league. Egos need to be left at the door. Sacrifice is a necessity.

“It’s been an adjustment period,” Tatum acknowledged. “At some point this year everybody’s gonna have to sacrifice. Essentially we’ve probably got six starters. And you can only play five, only five guys can finish the game. So between those six guys, any given night somebody might come off the bench, somebody might not finish, and it’s on all of us to understand that whoever’s night it is it’s for the better of the team. And we really have to buy into that. And it’s not easy sacrificing but it’s something we all have to do.”

To the Celtics’ credit, their stars have said all the right things in camp. Porzingis has come in with the perfect attitude. Holiday knows what it takes, having won a championship two years ago. Horford, who is likely to come off the bench for most of the season, has embraced that role.

It’s all for one reason.

“Most important thing is winning,” Brown said. “I think everybody is at that stage in their career for the most part, so I think that we all understand that. … From top to bottom, we just have to trust each other and make the right reads. We have great players and do what we do. The game will tell you who’s going to make the sacrifice and who’s not. It’s going to switch up from time to time. All our guys gotta be willing. The only thing that matters is winning.”