Galvanizing his teammates has been a critical element to helping coach Joe Mazzulla’s quest to build this new roster into a contender. Their journey together enters another chapter. This is Mazzulla’s fourth season as coach and their relationship is something Tatum doesn’t take for granted.

“It’s been great, I love Joe,” Tatum said of his relationship with Mazzulla. “I love him to death. He’s impacted me, my life on and off the court. I think that’s just who he is. He wants to positively impact everybody, making us better basketball players, make our team better, the organization better. He just cares about you as an individual. He really shows that every single day and it’s cool to work with somebody like that.”

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Tatum has had no restrictions in practice and appears to be back to himself after returning in March from a torn Achilles. It’s uncertain whether Tatum will be on a games restriction this season.

“I feel great,” he said. “Sixteen months (since the injury). I came back last March, I was cleared but mentally and conditioning standpoint, I wasn’t myself. I think for me, when I came back it was great from a mentality standpoint, just to get over that hurdle, even if I was at 80 percent of myself knowing I could still be effective.

“Going into the offseason, knowing I had the whole summer to get my body right and get into the rhythm of playing basketball, I feel so much more confident from a mental standpoint and physically than I did last March. That’s how it should be. It’s a long journey from the injury I had and I feel great.”

Working on shots

Two-way swingman Dillon Mitchell has spent his early Celtics tenure working on his jump shot. The club envisions the former St. John’s product being a 3-and-D player, meaning a plus defender who can make occasional threes. He entered the league as a plus defender but is now trying to reform his jumper.

If Mitchell can become an offensive threat, it’s possible to earn minutes on Mazzulla’s second unit.

“The little time we’ve had, how much my form has changed,” Mitchell said. “It’s helped me with a lot of confidence moving forward.”

Mitchell said when he and Chris Cenac were drafted in June, they went straight from the airport to the practice facility for a workout. Mitchell and Cenac are part of the Celtics’ future and they are being schooled vigorously during early training camp.

“It’s been immediate and it’s been every day,” Mitchell said. “There’s no days off. Every day you get it in, whether it for a short or a long run.”

Cenac, 19, has been working on his perimeter shot and learning from veteran teammates such as Mitchell Robinson and Neemias Queta.

“The NBA is like more attention to detail, little things,” Cenac said. “It’s more mental. It fits my game perfectly and I’ve been having a lot of fun, playing with these guys, learning from them. We’ve been pretty much working on everything.”

One spot left

The Celtics will travel to Cleveland from Charleston, S.C., on Wednesday as they begin to determine roster spots and roles. There remains one open two-way spot and three players — Devin Carter, Tucker DeVries, and Milos Uzan — appear to be in the running. Former Maine Celtic Hayden Gray, who played one game last season for the Jazz, is back with the club and could return to the G League team. The Celtics also have one roster spot remaining that is not likely to be filled during camp … The club officially named former guard Phil Pressey as the coach for Maine for the second consecutive season.

Gary Washburn is a Globe columnist. He can be reached at gary.washburn@globe.com. Follow him @GwashburnGlobe.