Jaylen Brown

Boston Celtics' Jaylen Brown has already impressed his older teammates.

(AP Photo/Jessica Hill)

BOSTON -- Watch the Boston Celtics bench after Jaylen Brown's next highlight play. Isaiah Thomas might jump nearly onto the court. Avery Bradley might scream until veins pop out of his neck. Marcus Smart might hop up and down like a child who just unwrapped the perfect Christmas present.

Players should always show so much exuberance for a teammate's accomplishments, but all it takes is one look to see the veterans have taken a liking to Brown. It's not just that the older Celtics think Brown will help the team immediately, or that they enjoy watching Brown's high-flying dunks. They do, but they are also struck by the rookie's maturity and work ethic.

"First of all, Jaylen is a very special player," Bradley told MassLive. "Not only a very good basketball player, but even a better person. And he's going to be a good player."

Before continuing, Bradley laughed for effect.

"Man, that's all I can say," he said. "He's going to be really special."

Brown's just 19. Despite his growing collection of highlights, he still makes silly mistakes every game. He isn't even close to whatever he will become. How can you be sure he will be really special?

"First of all because he's just a freak already," Bradley said. "He comes in every single day, working hard. He just has to learn the game and learn how to work even harder on the defensive end. And I feel like he's going to prove a lot of people wrong. Whoever thought whatever they thought about him or didn't know much about him, he's going to show everybody."

Four months ago, Celtics fans booed when the team introduced Brown as the No. 3 overall pick. Monday night, he received a loud ovation before checking into his first preseason game. The public is coming along already.

So are the Celtics.

"I wasn't as smart as him (at that age)," said Jae Crowder. "I wasn't as heady as he is. Physically I could play basketball, but I just didn't have the tools up top at the age of 19. I had to go through college and I had to go through a lot more obstacles to get to where I'm at today. But he has his head on right, he thinks properly, he works. He's become more of a professional earlier than I was.

"(He's uncommonly mature for his age) for sure because a lot of guys come in and are behind the curve a lot mentally. We're not talking physical, we're just talking mental, and the game here at this level is a lot mental. And that's one thing he brings with him. His mental approach is where it needs to be."

Entering training camp, Celtics head coach Brad Stevens intended to simplify things for Brown, hoping to bring the rookie along slowly. Instead, the coaching staff pivoted quickly, deciding not to limit Brown's versatility. He has played the wing in big lineups and power forward in smaller units. He has guarded Frank Kaminsky, a 6-foot-11 big man, and Carmelo Anthony, one of the best scorers alive.

After allowing Kaminsky an easy baseline drive out of the post, Brown went to the tape to watch film of his defensive possessions. Though he has played power forward for a large chunk of his preseason minutes, he said he rarely played there during his lone college season. Learning how to guard bigger guys is an adjustment, but Brown doesn't sound too concerned.

"Kaminsky's not -- I don't think he's stronger than me," he said. "So he's got a size advantage, but if I do my work early then he's pretty much beat. He got me on a couple plays and he's a really good player, but I feel comfortable guarding the 4."

During interviews, Brown sounds like a self-aware optimist. He can shift from listing all of his current flaws to stating he intends to become a top-five player one day. While discussing his growth, he can sound almost like Stevens, repeatedly stressing a focus on daily work rather than results.

"Coach said something to me ... that really helped me out," Brown told MassLive last week. "He said once you get in a rhythm and once you have some more games under your belt, you'll do less thinking and the game will tell you what to do. So I trust the game of basketball and I trust myself."

Brown also trusts Crowder and Bradley, the two veterans he has leaned on the most.

"Everything," Brown said of what he's learning. "Off the floor and on the floor I'm learning from Jae. Just how to be a pro, how he handles himself and things like that. I'm just picking up how to be a vet. The way he moves, the way he orchestrates everything, he's efficient. He doesn't really waste a lot of time because he has a lot of things he has to do. So I'm getting better at stuff like that. On the floor, same thing. How to be efficient, how to pick your spots, how to be aggressive, when to shoot, when not to shoot, when to attack, when not to attack. Get up the floor. Certain things like that, you just watch him, talk to him, pick their brains, and then you learn."

Much to the delight of All-Star teammate Al Horford, Brown can accomplish some rare athletic feats already. Everybody knows he can fly, but he needs to recognize when and where he should.

"Just finding a rhythm in the game," Brown said. "Just knowing when to attack, knowing when to be aggressive, knowing when to go, knowing when not to go. Sometimes I go and it's not the right time to go, and sometimes I should've went and I didn't. So it's just having that balance and trying to figure that out. And I'm sure I will. I'm almost 100 percent positive I will."

The latest episode of the Locked on Celtics podcast focuses on some rumors (sort of) and the race for the final roster spot. Listen to the episode below. You can also go to the show page on Audio Boom, download the Audio Boom app for your phone, and subscribe on iTunes or Stitcher.