Darren Erman will go from coaching the New Orleans Pelicans in the NBA to taking charge of the Celtics’ G League affiliate, the Maine Red Claws. Erman sees the move not as a step back but another opportunity to improve his chances of being an NBA head coach. RICK SCULEN/ASSOCIATED PRESS/FR157181 AP via AP

One day last week, as his wife Brittany wrote thank-you notes following the recent baby shower for the couple’s first child, Darren Erman sat alongside her and devoured G League game film.

For Erman, who has spent more than 10 years as an NBA assistant coach working with the likes of Paul Pierce, Kevin Garnett, Stephen Curry, and Anthony Davis, this career shift could appear to be a small setback. But the new head coach of the Celtics’ G League affiliate, the Maine Red Claws, views the detour as a wonderful and essential opportunity as he pursues his dream of becoming an NBA head coach.

“Head-coaching experience is hard to come by,” said the 43-year-old Erman. “Everyone wants it, but if you’re a long-time assistant, it’s hard to get.”

For Erman, who joined Maine after spending four years as the associate head coach of the New Orleans Pelicans, his deep history with the Celtics made this move even easier. This will be his third stint with the organization, and Boston’s upcoming purchase of the Red Claws will bolster the connection of the two teams.

Yes, it will be an adjustment to go from flying on private charters and staying in five-star hotels and training NBA All-Stars to riding buses and molding NBA dreamers, but it is also a somewhat fitting shift for Erman, because his route to this point was quite unorthodox anyway.

The Louisville native is 5 feet 8 inches tall and never played varsity basketball in high school. He graduated from Emory University and then went on to Northwestern Law School before working at a firm for three years.

But all along his passion for the game was stirring. He began sending letters to college coaches offering his assistance, but lawyers whose only basketball experience came as a student coach at Emory were not in high demand.

So, when Erman was 27, he left his six-figure salary and got a job as a teacher and assistant basketball coach at St. Anthony High School in Jersey City, working for the legendary coach Bob Hurley Sr.

And an even more important connection was forged that summer, when Erman was working as a counselor at Seeds of Peace, a Maine camp for teenagers who come from areas of conflict around the world. There, Erman met then-Nets forward Brian Scalabrine, who was brought in as a guest speaker. Erman sensed opportunity and offered to work at Scalabrine’s basketball camp, and, before long, an unlikely bond was formed.

Erman told Scalabrine that he wanted to become an NBA head coach someday, and Scalabrine found his big dreams endearing and, well, sort of ridiculous.

“I said to him, ‘You’re not going to make it,’ ” Scalabrine recalled. “There’s no possible way you’re going to make this, because I think you’re naïve to what this business is about.”

Erman mostly shrugged.

When Scalabrine went to watch St. Anthony play, he was in awe of the way Erman orchestrated the defense as well as how he communicated with the players. Erman ultimately became Scalabrine’s skills trainer and, basically, personal assistant.

“He just became my guy,” Scalabrine said. “He became very much an all-purpose individual, and that’s how the first few weeks of our relationship grew. I was around him basically 24/7 for two weeks and I’d literally just met the guy.”

When Scalabrine signed with the Celtics in 2005, he told Erman to come to Boston with him. So he did.

Erman met Scalabrine for so many evening workouts at the Celtics’ practice facility that most of the other players just assumed he was a member of the coaching staff. Guard Tony Allen thought that Erman was the son of a famous coach, and so sometimes he would ask Erman how his father was doing.

Before long, players such as Allen, Rajon Rondo, Delonte West, and Ryan Gomes were asking Erman to meet them at the practice facility for late-night sessions. They’d see Erman waiting outside for them and assume he was just being polite, but the truth was he didn’t have a key to the gym.

Allen’s presence was particularly important, because he was close to the future Hall of Fame forward Paul Pierce, and before long Erman was rebounding shots for both of them.

“Tony used to joke around and tell me that I’ve got to make Paul my guy, not him or Scal,” Erman said with a chuckle.

Celtics co-owner Steve Pagliuca was so impressed by Erman that he asked him to start working out his teenage sons, too.

In the summer of 2007, Erman helped out Boston’s Las Vegas summer league team as a kind of volunteer assistant, and that September he was officially hired. Danny Ainge and head coach Doc Rivers initially gave him a consulting role in the front office, but after a few weeks he became part of the coaching staff, which Erman’ preferred.

The Celtics won an NBA title during Erman’s first season, and he developed a reputation as a defensive specialist with unusual attention to detail.

In 2011, he was hired as an assistant with the Warriors, where he would work with up-and-coming stars Stephen Curry, Klay Thompson, and Draymond Green well before they turned into dynasty-makers. Erman was tasked with running the defense, and he also drew up most plays during timeouts. He was fired in 2014 for a violation of company policy. Erman allegedly recorded at least one conversation involving Warriors employees, although he was was quickly hired afterward by Ainge and the Celtics.

Once again, Erman was briefly put in a front office role, this time as the director of scouting, before ending up as a coach after Ron Adams departed for Golden State. The following year, the New Orleans Pelicans gave Erman the break he had been working toward when he was named associate head coach, the top assistant to head coach Alvin Gentry.

Darren Erman left a six-figure salary as a lawyer to follow his passion for basketball. Tyler Kaufman/Associated Press/FR170517 AP via AP

For the first time, Erman had to essentially prepare for games as if he was also the head coach. In 2016, Gentry missed a preseason game because of an illness and Erman slid into the primary role.

Later that season, Gentry was ejected in the second quarter of a game against the Clippers, and Erman was ready.

“I had to think about, ‘OK how many timeouts do we have? What are our rotations? Who’s been playing? Who needs to be subbed?’ ” Erman said. “So I went into every game thinking like that.”

In New Orleans, Erman maintained his ties to the Celtics. Ainge, Pagliuca, assistant general manager Mike Zarren, and director of player evaluation Dave Lewin were among those who attended Erman’s wedding last summer. (This connection did not do the Celtics any good during their pursuit of Davis, however, as Erman had no say in those decisions.)

Erman and Lewin, who previously also served as the Maine Red Claws’ general manager, used to talk about the possibility of Erman coming back to Boston someday to lead the G League team.

But after David Griffin was hired as the Pelicans’ general manager last spring, he began a bit of an organizational reshuffling, and Erman and New Orleans parted ways. Erman had other opportunities to become an NBA assistant, but he worried that would not get him any closer to his ultimate goal of becoming a head coach.

During a panel discussion at the NBA summer league in Las Vegas, Erman listened as several young general managers said how much they value previous head coaching experience when making hires for top jobs, even if it comes overseas or in the G League. That resonated with Erman.

So his enduring connections with the Celtics, and the chance to become a head coach for the first time made the Red Claws an appealing option. Some would consider Erman overqualified for the job, but he doesn’t look at it that way.

“For me, I hope I’m qualified enough with learning the G League,” he said. “Like, I’m trying to learn it.”

Added Lewin: “It speaks to his desire to grow and it speaks to his believing in himself. It speaks to how much he loves to coach basketball and wants to be a head coach. He doesn’t want to just be around basketball, with the travel and the prestige. He wants to coach basketball.”

With the advent of two-way contracts, which allow NBA teams to essentially stash two players on G League rosters, the connection between the leagues has continued to balloon, making a role like Erman’s more essential.

He spent a week in August meeting with Celtics rookies and training camp players who will likely spend the bulk of the season in Maine. He was encouraged by the possibilities.

Having previously worked under Brad Stevens, he has a good idea of the coach’s system and preferences. And he is looking forward to putting his own stamp on games, too.

“I’m excited about seeing what he’s going to do as a head coach,” said Scalabrine, who was a groomsman in Erman’s wedding last summer. “He’s been in the system a long time and has some good ideas. I’m excited to see how he grows. Are there different things he’s going to try that no one else has tried? In the G League you’re allowed to try a little bit more. You can experiment.”

And for Erman, doing things a bit abnormally has always been his normal.