Boston Celtics guard Marcus Smart, center, looks to pass while being defended by Washington’s Kristaps Porzingis, left, and Rui Hachimura during an October 2022 game. The Celtics have acquired Porzingis from the Wizards in a three-team trade that involves sending Smart to Memphis. AP file photo

Marcus Smart was upset with the officiating, and then he got upset with his coaches.

It was Nov. 7, 2019, during the third quarter of an otherwise ordinary early-season Boston Celtics win over the Charlotte Hornets when Smart picked up his fifth foul. He was removed from the game by then-coach Brad Stevens.

As he walked off the floor and past the coaching staff, a clearly miffed Smart voiced his displeasure and stopped to clap at them before taking a seat.

Stevens didn’t take offense. It was all part of the Smart experience.

“This is the part about Marcus that I love,” Stevens said after that game. “His fire, his competitiveness. If there’s a moment where he’s upset with us, that’s all part of it. We move on pretty quickly. We’ve been together a long time. I’ve been yelled at before and that’s OK.

“I love him and I trust him.”

That final sentence became a rallying cry and motto for a Celtics fanbase that grew to adore Smart, who left it all out on the court with his unique style of play over nine seasons and not only came to embrace Boston, but embody the city and franchise.

“I love Boston and Boston loves me,” Smart said when he signed a contract extension two summers ago.

Those sentiments haven’t changed even after the shocking circumstances of Wednesday night, as Smart’s time in Boston came to an abrupt end after nine seasons when Stevens struck a trade to send the point guard and franchise cornerstone to Memphis in a deal that landed Kristaps Porzingis. In fact, it’s only been highlighted in the hours since the stunning trade, with fans mourning his departure on social media.

It was a move that not only stunned the fanbase but emphasized the harsh reality of this business like few can.

Stevens knows Smart and how important he is like no other, having coached him for seven seasons before moving to the front office as the president of basketball operations in 2021 and inking him to that extension. There were strong ties developed over nearly a decade. But Stevens removed the emotional element out of it to make the kind of necessary move that has made him a shrewd general manager that’s required to run a successful team.

In two years, Stevens has already made a number of keen moves. He brought back Al Horford two weeks into his new job in a trade that sent Kemba Walker and a first-round pick out. He executed a trade deadline deal in 2022 to acquire Derrick White, a move that was criticized at the time but has worked out. He made a deal to get Malcolm Brogdon last summer, then nearly traded him away on Wednesday after a successful season before the initial Porzingis deal that would have sent him to the Clippers broke down.

Stevens clearly isn’t afraid to make a seismic change in pursuit of a championship, and the Smart trade represented his boldest move yet.

It took serious fearlessness to trade Smart, even if on paper it doesn’t look that way.

Smart never popped in the box score. He didn’t even become the full-time starting point guard until two years ago. But his impact was felt in deeper, intangible ways. Hustle plays, so many of them. His leadership. His work in the community. He was the glue that was a constant for the Celtics as they rebuilt following the departures of Paul Pierce and Kevin Garnett and became a top championship contender.

Smart certainly had flaws, and there were several frustrating moments with him. A championship ultimately proved elusive in his time here, and after knocking on the door for several years, Stevens made the tough decision to create change by moving on from him. But it shouldn’t — and won’t — be lost how much Smart meant to this city and franchise to get them to this point.

Some other thoughts on the fallout of the Smart trade:

• How the Celtics approach their commitment to Porzingis will be interesting. The big man opted into his $36 million player option to complete the trade and is currently entering next year on an expiring deal. He’ll be eligible to sign a two-year, $77 million extension in July, but that carries obvious risk. While Porzingis is coming off a career-best season in which he was mostly healthy, his injury history is concerning. Also, that’s a big commitment to make to a player before he plays a minute on his new team.

It may make more sense for the Celtics to wait until after the season to determine if Porzingis fits and is worth that extension. But then the new collective bargaining agreement — which creates difficult salary cap restrictions — comes into play, so it’s certainly possible this becomes a one-year rental.

• There were several reasons the Celtics lost to the Heat in the playoffs, and one reason is that they were out-toughed. It’s feasible that the C’s lose both Smart and Grant Williams — two of their toughest-minded players — this summer. Porzingis, meanwhile, has played in just 10 career playoff games and has never made it out of the first round. This is certainly a new situation, but he’s not exactly playoff-tested and it’s unclear how he would perform in those pressure moments.

• The departure of Smart opens the door for Derrick White to be a fixture after he emerged as one of the Celtics’ best players last season. His significantly improved play, for better or worse, made Smart expendable. White regularly had to play a backseat to Smart in late-game situations even though he was one of Boston’s best players in crunch time, but depending on what other moves Stevens makes, he should be in those lineups every night now.

• Without Smart, there’s a clear leadership void. Enter Jayson Tatum and Jaylen Brown. While those two are obviously the Celtics’ best players, Smart was still the unquestioned leader. Now it’s Tatum and Brown’s turn to step up and truly make this their team.

• Smart would not be gone if the Clippers didn’t raise concerns about Brogdon’s health in the initial three-team deal and backed out. Brogdon suffered a serious forearm injury in the Eastern Conference Finals and his status looms large as the C’s shape their roster this summer.

• There’s a case to be made that the Celtics sold high on Smart and took advantage of his value that may not be higher going forward. Smart admittedly declined defensively last season after winning Defensive Player of the Year in 2022 and the C’s have a surplus of guards that made it easier to part ways with him.

The return for him may be better than expected. Porzingis, if healthy — big if — gives the Celtics a significant boost and upgrade in their frontcourt and allows them to be more balanced, and they also netted two first-round picks despite the deal nearly falling apart at the last minute. That’s a win for Stevens.