Check out some of the most talked about offseason moves and what the Celtics' new roster looks like headed into the 2017-18 season. (0:45)

BOSTON -- For the final night of the Boston Celtics' training camp sojourn last week in pristine Newport, Rhode Island, Al Horford herded nearly half of Boston's roster to Sayers Wharf for dinner at The Mooring Seafood Kitchen & Bar. After a pair of intense two-a-day workouts, players relaxed while nibbling on the restaurant's famed Bag of Doughnuts (lobster, crab, and shrimp fritters) and shared stories while mindlessly building the off-the-court chemistry this team so desperately needs after an unprecedented roster overhaul this summer.

When the meal was over, players stepped out into an unseasonably humid night, but Horford had one small request: a photo. Horford is not a big social media guy, but he wanted to document the outing, and smiling players huddled for a snapshot that quickly landed on Horford's Instagram account.

Two good days of practice. Time to break bread! A post shared by Al Horford (@al_horford) on Sep 27, 2017 at 6:42pm PDT

Unfortunately, the bright lights from historic Thames Street in the background washed out much of the photo. The comments section turned into a roast of Horford's phone with commenters wondering if he had snapped the pic on his Motorola Razr. Even second-year swingman Jaylen Brown couldn't resist a jab, asking Horford if used his "picture phone" to take the snapshot.

"I think Al still has a flip phone, man," the 20-year-old Brown would joke the next day. "Al still lives in the Stone Age a little bit. We ought to get him a little bit more hip to what's going on."

Poor Horford, the oldest player on Boston's roster at age 31, had already picked up the bill despite the presence of some of the Celtics' freshest faces, including No. 3 pick Jayson Tatum ("We don't [make rookies pay] here; we take care of our rookies," Horford said). Still, he laughed off the phone barbs. Horford knew the night's memento wasn't perfect, but he was glad to have something to remember it by.

"Oh my gosh, the picture was awful," said Horford, who, for the record, has a perfectly functional, recent-model iPhone. "But I was like, you know what, we didn't take a picture all dinner, which we probably should have. I'm not very engaged with social media, but I was like, 'Let me make an effort'. And the picture didn't come out well. I said, 'Let me try to filter it up.' But it didn't look any better, so I was like, 'It's still going up because we can't get another picture.' I've been getting killed about that."

Horford is the only starter set to return for a Boston team that brought back only four players from last season's 53-win team. While it took him much of his first season in Boston to truly feel comfortable in his new surroundings, Horford has made it a priority at the start of camp this year to make his new teammates feel as relaxed as possible.

Dinner was just one way Horford has tried to help build chemistry, on and off the court.

"To me, for all the guys to feel good and to feel acclimated, that's important," Horford said. "The quicker that we're able to do that as a group, the better. I feel like we do have a lot of changes -- not just players, but trainers, strength coach, everything. All the change, everything is new for all of us. I want to make it easier on everyone."

Horford has always been a quiet leader, but he understands the importance of getting everyone on the same page at the start of this season. And while his teammates might tease him about his phone, they rush to answer when he calls.

"Al is one of those guys that does the right thing all the time. He's very consistent in that," Brown said. "Any time he says something to me, I'm all ears."

Echoed head coach Brad Stevens: "I've always really respected Al for every which reason, but the No. 1 thing is, whenever he talks, it's worth listening to. He really has a way about him that he picks his words carefully, he picks his times to speak carefully. I haven't seen a change in personality -- he hasn't turned all of a sudden into this person who is talking 24 hours a day -- but clearly, when he speaks, everybody listens."

Al Horford is entering his second season with the Boston Celtics, and his 11th season in the NBA. Brian Babineau/NBAE/Getty

The Celtics knew they got one of the league's most skilled big men when they inked Horford to a four-year, $113 million max contract at the start of free agency in 2016. And it didn't take long to see just how impactful he could be on the court.

Boston coaches excitedly nudged one another on the bench throughout the Celtics' first preseason game last year on the campus of University of Massachusetts. Stevens already liked to initiate offense through his bigs, and here was Horford spraying the ball around the court to open shooters.

Throughout his career, there have been two constants with Horford: winning (he has made the playoffs in each of his 10 seasons) and making teammates better. So maybe it should come as no surprise that the Celtics elevated to the top of the Eastern Conference standings last season while a player like Isaiah Thomas had a season in which he finished fifth in MVP voting.

"I don't think it's a coincidence that so many of our perimeter guys had the best years of their career last year," Celtics president of basketball operations Danny Ainge said. "I think Al, the way he plays, how unselfish he is, his experience ... he's the kind of guy who has the reputation around the league that guys want to play with him."

Horford played a noteworthy role in convincing Gordon Hayward to sign in Boston this past summer. Horford flew to Boston to be part of the early July recruiting process, had breakfast with the Haywards, then tagged along for the pitch that included a stop at Fenway Park.

"[Horford] was in a similar situation, where he had spent his whole career in another organization and had a chance to change," Hayward said. "I talked to him about that, about making that leap and making that decision. I talked to him also about being someone in a similar situation, as far as having young kids and what it was going to be like living in Boston, living with some of the challenges a big city presents, and some of the benefits of a big city."

Hayward continued to gush about Horford's on-court skills and said he's eager to share the floor with him. While Boston added two All-Stars this summer in Hayward and Kyrie Irving, there are many in the Boston organization who believe Horford is maybe the most important piece to Boston's success.

Irving is Boston's best offensive weapon (and Thomas showed last season how important it is to have someone like that), Hayward is Boston's best all-around player, and Horford is the key to making it all work.

Al Horford's veteran presence has been a positive influence on younger teammates such as Jaylen Brown. CJ Gunther/EPA

During one of his media availabilities last week, Irving was asked if he had seen plays and sets in which he and Hayward could thrive together this season. Irving's face lit up and a big smile appeared. When a similar question was put to Horford recently, asking if he has seen glimpses of how Boston's new Big Three can help one another, his face, too, lights up. Horford can't muffle a smile as he begins to talk.

"Yeah. That's why I'm so excited," he said. "Obviously, when we got Kyrie, I was excited. But once we get in here and we start working, there's a lot of potential here. It's exciting."

Irving, Hayward, and Horford were often spotted together on the sidelines at training camp last week. Horford marvels at how fast his teammates have picked up the offense but also knows they're probably overwhelmed as Stevens inundates them with information. Horford also sees last season's version of himself in the newcomers and wants to help them get up to speed as fast as they can, especially with a shortened preseason.

Still, Horford sees what's possible and it excites him. And he's willing to do whatever it takes for Boston to play its best basketball.

Horford was spectacular in the playoffs last season, playing a lot of the small-ball 5 that he'll play this season for a Celtics team that lacks experience up front. But his postseason stat line didn't jump off the page while averaging 15.1 points, 6.6 rebounds, and 5.4 assists over 33.9 minutes per game.

The stats never quite tell the story with Horford. It was telling that, when he coached the East All-Stars last season, Stevens made sure to note how he believed Horford should also be there for the Celtics.

Which raises the question that we always come back to with Horford: What does the casual fan not know about him?

We put that very question to Celtics assistant coach Jay Larranaga, who spends more time than anyone in the organization with Horford as his player coach. On game nights, the two can often be seen crunching film together before Larranaga leads Horford through his typical pregame shooting routine.

Larranaga pondered the question for a bit before answering, and it was clear he wanted to pick the right words.

"I would say, on the court, people probably don't realize what an unbelievable help defender [Horford] is," Larranaga said. "You might see a blocked shot at the end of games, but it's how he is in the right position, always. He's covering for teammates constantly. I think people see how unselfish he is, offensively, but he is equally unselfish defensively, and has an equal impact on his teammates' performance.

"Then, off the court, I think, like a lot of the great players and a lot of the players that have been able to sustain success over a long period of time, I think they don't realize how much time and energy he puts into his craft. How much he prepares. His preparation starts every morning when he gets up with what he's eating, he's constantly learning and trying to get better. I think people have an idea and say, 'Oh, Al's very professional.' Being professional is like a full-time job and his full-time job is not just during the season, it's in the offseason. I think people have an idea but not to the extreme."

Georgia native Brown spent much of the summer working out with Larranaga and Horford near Atlanta, where Horford spent his first nine NBA seasons. Brown might elevate to a starting role this season, but you can see the impact of simply being around Horford. Brown is eager to be a sponge around the veteran.

Heck, he might even be willing to downgrade the megapixels on his camera phone to be more like Horford. Yes, he recognizes a quality role model and leader.

Said Brown: "How [Horford] carries himself is how I would like to carry myself."