NEWPORT, R.I. — There are still 521 days before he can legally drink alcohol if he goes out for dinner and a sip after a home game. But the Celtics can’t wait nearly that long for Jayson Tatum to come of basketball age.

Before yesterday’s second session at training camp, we asked Brad Stevens flatly whether his club would need a contribution from someone like Tatum if it is to reach its potential.

“Of course,” said the coach. “I don’t think there’s any question about that.”

How big a contribution will be dependent on how well Tatum grows into the NBA game. With veteran stars to light the path, the Celtics should be able to compete well with any opponent’s core; if Tatum is a consistent threat by the end of the season, they should be able to put the hammer down.

Al Horford is expecting him to be an integral part of the rotation.

“Yeah,” he said. “No question. No question. He can score the ball. He rebounds pretty well. He’s shown it here the first couple of days. And he has a good sense on the court. He has a good feel of playing, and sometimes that’s harder for rookies. It takes them time to find their place. It’s early, but I have seen those things from him and I like that.”

As for how Tatum ranks with others Horford has watched take their first professional steps in a camp, well, Tatum is doing pretty well on that scale, too.

“You know, it’s hard to tell by the first couple of days,” Horford said. “But just looking at him and from summer league, I’d say he’s probably got to be up there in my book for guys to be ready and contribute.

“He comes into a unique situation, being such a high pick and coming to a team like us. If he was going to a bottom team, I think we would all agree that he would be the main guy and playing a lot of minutes. So he has a different situation, a different challenge. But I feel like he’s taking it well, and for him it’s got to be a day by day thing and making sure that he gets better and more comfortable. But he’s as ready as I’ve seen any rookie.”

Stevens, meanwhile, is understandably keeping a lid on the steaming expectations.

“He’s going to be a really good NBA player for a long time,” he said. “I think any other prediction would be probably, you know, too early to tell. But I think he’s going to be a really good NBA player for a long time. He brings a lot to the table, and he’s really smart. He has a savvy that I think you can tell when he’s out on the floor.”

And, yeah, he’s still just 19 with a year at Duke between high school and preparation for opening night in Cleveland against LeBron-flipping-James.

“You know, everybody talks about the one-and-done thing in college,” said Stevens, “and I’ve been impressed (with) Jaylen (Brown) and Jayson and how advanced and ready they are to really take on challenges, to be excited about challenges from a work ethic standpoint, from a maturity standpoint and all of those things. There’s a lot to learn playing in the NBA for the first time when they get here, but I’ve been really impressed by that.”

Tatum may be a bit reticent with the media, polite but not expansive, but from all accounts around the team, there’s nothing reserved about him when he’s on the court.

“I’m getting better each practice, getting more comfortable, so that’s a good thing,” he said. “Everything’s being thrown at you faster because we play on Monday and we play regular season pretty soon, so everything’s just quicker. . . . The style of play is faster, but that was expected.”

Quicker, too, is the orientation period. School is in session at nearly all waking times.

“Everybody has an iPad and they send us clips,” Tatum said, “and I watch film with the assistant coaches, and I think that’s very helpful, just seeing it broken down on video.

“You learn just as much when you’re on the bus and in team meals as you do in practice. We just sit and talk about a lot of different things, and these guys, most of them know so much. They’ve been around the game for such a long time.”

As for what knowledge specifically has been gleaned, he said, “Just everyday things, how the road schedule is and how that’s tough and how recovery is key and how their rookie seasons went and how they learned things along the way.”

Best advice?

“Just stay focused and stay with it, because I’m 19 and this is my first season,” Tatum said. “It’s a long season, and I have guys around here that are willing to help me when times are tough.”

Times will most certainly be tense for Tatum when the Celtics are in the playoffs next spring and his teammates look to him. He acknowledges that there is pressure.

“Yeah, there is,” he said, “and just the nervousness of your first season in the NBA. I think all of it plays a factor. So yeah.”

It comes with the territory when you’re 19 and a team bent on the NBA Finals is hoping you’ll play a factor.