Jaylen Brown, 7, scored 25 points and had two blocked shots for the Celtics during their victory over Toronto during the home opener last Friday. Michael Dwyer/Associated Press

Several players have looked indispensable as the Boston Celtics opened the season with two wins in their first three games.

If Kemba Walker doesn’t get hot in the second half against Toronto last Friday and carry that over through Saturday’s game in New York, is it not possible the Celtics are looking at 0-3 with the Milwaukee Bucks coming to Boston on Wednesday?

Where would the Celtics be if not for rookie Grant Williams giving them high quality inside minutes and playing above his size?

Jayson Tatum has given them 20.3 points a night and improved 3-point shooting. Gordon Hayward has looked a lot more like Gordon Hayward. And Marcus Smart has been his usual demonic self on defense, though he’s taken 19 3-pointers (26.3 percent) to just eight 2-pointers (50 percent).

Rob Williams has given them good offensive looks and shown flashes at the other end of the floor, and Enes Kanter had a good opening night (12 points, 6 rebounds in 25 minutes) before being sidelined with a bruised knee.

But in all of this, one should not overlook the efforts of Jaylen Brown. Indeed, it was Brown’s limited playing time because of foul trouble that may have been the key factor in the lone loss.

The 76ers, in the end, looked like the better team in the season opener, but for a good stretch of the night, the Celtics had the upper hand, and Brown was in the middle of that with his ball pressure. Philly was taking a bunch of bad shots, and it wasn’t until Brown went out with his fourth foul early in the second quarter and fifth foul early in the third, that Ben Simmons, still allergic to outside shooting, began to get downhill on easier-than-they-should-have-been drives to the basket.

The Sixers loosened up when Brown left the floor, and neither he nor anyone else in green and white seemed capable of slowing them down consistently after that happened.

Brown came back with 25 points (and two blocked shots) against the Raptors. Then 19 points, a block and a steal in just 27 minutes against the Knicks.

He’s shooting 50 percent from the floor and is driving twice as much as he did last season. (Small sample size, but still ….)

In his fourth season, with the security of a contract extension in hand and knowledge from the last two very different Celtic seasons in his head, it’s a different Jaylen Brown.

“I think I’ve gotten better,” he said. “I had a great experience at USA Basketball, and I think as I’ve gotten older, the game has slowed down. I’m better at making reads now.

“I believe in myself. I believe in my team.”

Brown was a mature 19-year-old when drafted, and now, after turning 23 last week, he is even wiser.

“I think that’s how life’s supposed to go,” he said. “Every year you’re supposed to garner experience and mature a little bit more — on the court and off.”

And where he acknowledges that trust was lacking around this team last year, he recognizes its importance even more.

“I think it’s everything – trusting yourself, trusting your ability, your coach having trust in you and your ability,” Brown said. “I think that makes a big difference. If you’ve got to look over your shoulder because you don’t know if the coach is going to sub you out or the coach doesn’t want you taking this type of shot, that can sometimes play with people’s minds and their games. But I think Brad (Stevens) has great trust in each and every one of us, especially with a little bit more freedom this year with less players. I trust in myself, and I believe in my coaching staff and my organization.”

As for what he needs to do this season, Brown said, “I think just be myself – on offense and defense. I think I need to just be aggressive, make the right reads, you know, take care of the basketball, be a leader of this team, lead by example.”

The way the Celtics underachieved last season may have scared some of the returnees straight, but it’s still far too early for judgments.

“I’m not trying to compare last year to this year – nor do I care to compare last year to this year,” Brown said. “But I’m happy. I think it’s all smiles right now. I think everybody’s excited, and we’ll see how that turns out.

“We definitely underachieved, but other than that, I’m not even really thinking about last year. The only thing on my mind about that is we didn’t achieve what we planned out to achieve. We’re acknowledging that, but everything else is water under a bridge. It’s over with.

“Our mantra for this year is ‘Just hoop,’ and that’s it.”

And Brown has been as important as anyone in carrying that flag.