Alex Barlow works with players during a timeout at a Maine Celtics game against the Windy City Bulls in January at the Portland Expo. NBAE via Getty Images

He helped train Tacko.

He repped the Red Claws.

He tutored Time Lord.

Five years after first arriving in Portland, Alex Barlow has been promoted to head coach of the Maine Celtics, the G League basketball affiliate of the Boston Celtics.

The team made the announcement on Tuesday, but Barlow, 30, received official notification about a month ago. He has known for much longer that the next rung on his coaching ladder would be in Portland.

“I’m definitely excited,” Barlow said by phone Tuesday during a break from Boston Celtics preseason training camp. “I’ve been wanting this opportunity since I got to go to Maine in ’17-18. It’s something I always wanted to do.”

Boston also promoted last year’s G League head coach, Jarell Christian, to general manager of the Maine Celtics to fill the position formerly held by Remy Cofield, who is now Boston’s scouting director.

Christian led Maine to a 10-2 start during the G League’s Showcase Cup segment followed by a 16-16 regular season.

“Our focus has been about developing talent in Maine, and that includes our staff,” Christian said in a prepared statement. “Alex has served this organization in various roles, and I know he is prepared to continue carrying out the values of the Celtics organization.”

Barlow becomes the eighth head coach in the history of the Maine franchise, known until 2021 as the Red Claws. He grew up in Cincinnati and walked on a Butler University, where he earned a scholarship and played point guard for Brad Stevens.

The Celtics hired Stevens as their head coach after Barlow’s sophomore year, but after graduation his old coach hired Barlow as a video assistant and he’s been with the Celtics ever since.

“Brad’s probably the person I’ve learned the most from,” Barlow said. “His demeanor, first of all. He never gets too high, never gets too low. Even on the sideline, he’s so even-keeled. I think the players always fed off that.”

Stevens is now president of basketball operations for the Celtics after eight seasons as their head coach.

“If I just ran all the late-game plays that he ran, I would never need to come up with one of my own,” Barlow said. “He was so good at that stuff. I learned so much from him.”

In Portland, Barlow served as associate head coach to Brandon Bailey in 2017-18, Darren Erman in 2019-20 and Christian in 2021-22.

From Bailey, Barlow learned defensive nuances and the importance of being organized. From Erman, he learned how to adapt to your personnel. From Christian, he learned how to lead and the importance of delegating.

With Erman as head coach, Maine ran wild … unless 7-foot-5 center and fan favorite Tacko Fall was in the game.

“When Tacko was in, we wouldn’t play quite as fast and we’d play through him,” Barlow said. “We had a very different team that I’ve had either in my time in Maine or in Boston.”

In 2018-19 Barlow served as something of a personal tutor to rookie Robert Williams III, aka Time Lord, who famously overslept an introductory conference call with reporters after being drafted and then missed a flight to Boston and the team’s first practice.

Over the summer Barlow was an assistant on Boston’s Summer League team in Las Vegas. He and his wife Belle (who played volleyball and basketball at Butler) welcomed a son, Colton, born in early July.

Two of the Summer League Celtics signed two-way contracts with Boston and are expected to spend considerable time in Maine. Guard JD Davison is a second-round pick (53rd overall) from Alabama who turned 20 on Monday. Center Mfiondu Kabengele (pronounced fee-ON-doo cabin-gelly) has NBA experience of 51 games over two seasons with Cleveland and the Los Angeles Clippers.

Kabengele, 25, is the nephew of Hall of Fame center Dikembe Mutombo and was a first-round pick in 2019 out of Florida State by the Brooklyn Nets, who traded him to the Clippers. He spent last season with the G League’s Rio Grande Valley Vipers.

“I love Portland,” Barlow said. “Great city, great food. It’s always fun getting to coach in the Expo, with a great fan base that loves their Maine Celtics.”

As he knows well, the Holy Donut is just across Park Avenue from the Portland Expo. He has a fondness for the maple bacon potato offering.

“It’s really good,” he said. “It’s an elite-level doughnut.”

The Maine Celtics are expected to begin their training camp in Maine on Oct. 24. They open the season at the Expo on Nov. 4 against the Westchester Knicks.