WALTHAM — Avery Bradley has watched a lot of rookies come and go, but the longest-tenured Celtics player never has seen one quite like Jaylen Brown.

“He’s a freak, man,” Bradley said yesterday. “He’s making a lot of plays that 19-year olds aren’t making.”

Brown’s athleticism was on display in Monday’s 120-99 win against the Brooklyn Nets, and his 12 points were second only to guard Isaiah Thomas. Bradley was stumped when asked who the 6-foot-7 Brown compares to in the NBA.

“That’s a good question. I can’t think of anyone off the top of my head, but I do know that he’s going to be a very special player if he continues to work hard,” Bradley said. “You can see it in the game in the plays that he’s making, how confident he is in his game. He’s just out there playing basketball, and a lot of 19-year olds aren’t doing that.”

The No. 3 overall pick’s play also has caught the eye of veteran Al Horford.

“I always get excited when he gets in the game because I just want to see what he can do, or what he’s going to do,” Horford said. “It seems like he’s always getting a highlight play, and I think that’s just a preview of what we’re going to see during the season.”

Like any rookie, Brown still is a raw product, but it hasn’t been difficult for coach Brad Stevens to find reason to put him on the floor.

“Nothing hard for me. It’s do you add value to winning? That’s how you fit into our group,” Stevens said. “We’ve got a good group. I like his progress. I like what he’s done thus far. I think we’ve thrown him into the fire a little bit at two positions, but ultimately that’s how we have to move forward.

“And hey, there’s going to be some growing pains with some of these young guys, too. You have to understand that, but if you bring something to the table that helps our team win, that’s what we have to consider first and foremost.”

Joining a seasoned C’s club that is expected to finish near the top of the Eastern Conference, Stevens said Brown just needs to embrace his role.

“I’m a big believer in this: Every one of these guys is here for a reason, and it’s about doing what you do well,” Stevens said. “And if you do that, you best position yourself to help earlier in your career. I’ve said from Day 1 with Jaylen, if he can defend a couple of positions, if he can make an open shot on the catch-and-shoot, and if he can drive or cut and figure out the times to do that, then those will be great separators for him because he has some gifts that will allow him to be on the court, with his body and his frame and his quickness and everything else.”

It’s easy for lottery picks to buy into their own hype, but according to Bradley, the most encouraging thing about Brown has been his attitude.

“He works hard, and he asks questions, and he’s here to get better every single day,” Bradley said of Brown, who will turn 20 on Monday. “I appreciate him for that, a young guy that has an open mind and just wants to work hard because that has to be your mindset coming into a team like this with good players like we have.

“He’s going to be a perfect piece for us.”

Not satisfied

Despite Monday’s win against the Nets coming by 21 points, Stevens was far from satisfied with his team’s effort.

“I thought we screened a little bit better. I thought we figured out how to move the ball a little bit better. Unfortunately we moved it to the wrong team too much in the first half,” Stevens said. “Then defensively we made some glaring errors that we need to work on.”

Three’s charm for coach

Executives around the NBA are starting to take notice of Stevens.

In NBA.com’s annual general manager survey, Stevens was one of three coaches to get votes as the best in the league.

Spurs mainstay Gregg Popovich was the runaway winner, garnering 83.3 percent of the vote, and Dallas’ Rick Carlisle was second at 13.3 percent. Stevens finished third at 3.3 percent.

Stevens was also voted third-best at making in-game adjustments (13.8 percent) and the No. 3 motivator of people (6.7 percent). He also received votes as running the league’s best offensive and defensive schemes.

However, he wasn’t patting himself on the back at practice.

“I didn’t even know that there was such a survey,” Stevens said. “It’s nice to be recognized by people that are in the league, but I never put too much stock in anonymous stuff. I think that ultimately it’s nice, but this league has 30 really good coaches.

“I think we all recognize that it’s about the players on the court, and hopefully I can just do my job to help try to maximize our group. It’s nice to be recognized, but at the end of the day, the minute you feel too good about yourself, you’ll be 30th quickly. This is a heck of a league coaching-wise.”