First look at the revamped Celtics has us intrigued

Jaylen Brown shows off some moves at media day.jessica rinaldi/globe staff

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CANTON — It’s not exactly the freshest analogy, I know, but it’s a correct one. Celtics media day in Canton Monday had a decidedly first-day-of-school vibe to it. Optimism was high. Everyone, even the fringe roster players who might be wise to start planning for winter in Portland, Maine, was full of optimism, sure that this will be their year.

Some didn’t have to establish their credibility. They arrived with popularity based on great feats achieved elsewhere. Kyrie Irving and Gordon Hayward — the former arriving via blockbuster trade, the latter as a free agent — are the new franchise cornerstones, and expectations aren’t exactly minimal for first-round pick Jayson Tatum, either. (His teammates rave about him.)

The new kids in town are already the big men on campus . . . or at least at High Output Studios’ campus, where media day moved this year from its familiar spot in Waltham. Everyone wanted to get a glimpse, to hear what they had to say, to talk about them reverentially when they’re not around.

Coolness comes easily for them. Irving especially, and it’s understandable why. He not only has a championship ring, but he hit the shot that secured it, burying a late jumper in Steph Curry’s face on the road in Game 7 of the 2016 NBA Finals to take down the 73-win Warriors and deliver Cleveland its first championship in forever and a day.

Here’s Al Horford, one of four Celtics holdovers from last year, on Irving: “I don’t think people understand how special he is.”

And here’s Jaylen Brown on playing with one of the most electrifying offensive players in the league: “It’s weird. Still is a little. I’ll let you know when it stops being weird.”

But the most interesting element about the first day is to see how everyone has changed over the summer.

Brown, the bright but wide-eyed first-round pick last year, suddenly carries himself like a veteran, which in a weird way he is: Only two players on the roster, Smart and Terry Rozier, have been Celtics longer. He does not seem to shy from responsibility. He has spoken to his teammates and president of basketball operations Danny Ainge about organizing a teamwide protest against racial injustice. He is referred to by former college teammate Jabari Bird as “the O.G.” — and Bird, a rookie, is older than Brown. He talks about his desire to guard the best player on the opposing team every night. He talks and looks (he has put on obvious muscle) like a confident five-year NBA veteran who knows the ropes.

He makes it easy to forget that he’s 20 years old. I can’t wait to see where this year brings him.

We’re not about to do Class Superlatives before this season even begins, but on the verge of training camp, the most interesting man isn’t one of the newcomers, but another of the quartet of holdovers: Marcus Smart. He has lost 20 pounds since the end of last season, and it seems to have come from a significant uptick in maturity at age 23.

He recognized that he was getting tired late in games, especially during the playoffs. His back seemed to ache more than a young athlete’s should. So he did something about it. He hired a chef, began working out like a man with something to lose besides a few pounds, and according to teammates is suddenly finishing at the rim and zipping all over the court.

“He’s athletic as all get-out,’’ said Brown.

Given that Smart was already a premier defender — though “I was basically an undersized 4 [power forward],’’ he joked — he could be a vastly improved and more reliable performer, one that brings the Celtics to another level, especially if he remains a physical force.

“My strength has never been lost,” Smart said. “There’s that weight that I lost, but the fat has turned into muscle. And now you add a little bit of quickness and more explosiveness, so now I can contest those guys more at the rim, instead of, once they get by me they’re by me.”

For some, this is the beginning of a chance to prove they belong, that they can run with the varsity. At times, it felt like Red Claws media day when the likes of Bird and Kadeem Allen, both rookies, took their turn in front of the microphones.

But there were poignant stories to be found. Shane Larkin, a former first-round pick who had some success as a rookie before injuries and ineffectiveness interrupted his plans, talked about how playing in Europe helped him find his old self.

“In my last couple of seasons in the NBA, I wasn’t the same player I was coming into the league,’’ said Larkin, who still is just 24. “To be honest, I lost a lot of confidence.

“I found it playing overseas, where the expectation of American players is that you’ll be the man. I remembered who I was. Now, I think this is a great opportunity to grow as a player. I mean, who doesn’t want to play for the Boston Celtics?”

Training camp will tell us whether Larkin can still play. But Monday told us he’s someone worth rooting for.

Oh, and of course we should note that everyone is wearing the same trendy new clothing. The Celtics’ new Nike jerseys, as crisp and white as they were under any previous brand, are sharp. And don’t sweat the new GE logo/patch. It’s unobtrusive. And it’s not as if it says “Chico’s Bail Bonds” or something.

They’re still the Celtics, still look and dress the part, even if the names on the back of the jerseys have changed. We know many of them now, even if they’re new to town. We’ll know others soon. And some we’ll never see again.

All we know for sure right now is that it’s going to make for a fascinating yearbook.