The Maine Celtics’ G League regular season so far has been a story of two halves: a red-hot start, followed by a scuffling stretch.

On Saturday against the Birmingham Squadron, the formula took form again.

Maine built a 17-point lead in the first half but saw it slip away in the second, falling 113-106 in front of an announced sellout crowd of 2,417 at the Portland Expo.

Kamar Baldwin led the Celtics (8-5), who have dropped five of six, with 23 points. Marial Shayok added 20 and Marvin Smith scored 16.

Dereon Seabron had 27 points and James Kelly Sr. scored 20 for Birmingham (4-12).

“We got stagnant on offense and quit moving the ball as much, so some of the 3s we got in the second half weren’t as good as in the first half,” said Celtics Coach Alex Barlow. “I think it was their switching, and they just played harder.”

The Celtics came into the game ranked second in the league in 3-point shooting, and those skills were on display early as Maine started 11 of 16 from deep and led 59-46 at the half.

But Maine hit only six of its last 22 3-point shots, and Birmingham pounced. The Squadron took their first lead of the game at the end of the third quarter, and though Maine surged back ahead 92-84 early in the fourth, turnovers and missed shots allowed Birmingham’s transition game to take control.

“They were doing a good job of switching and throwing different defenses at us, and we just got stagnant at times,” Smith said. “(It was) self-inflicted stuff that we can control.”

The theme of the game has been the theme of the season. Maine started the regular season 7-0 and several stars emerged. Luka Samanic, the 19th overall pick in the 2019 NBA Draft, leads the team with 23.9 points per game, while Shayok (20.3), two-way player Mfiondu Kabengele (20.0), Baldwin (15.7) and Denzel Valentine (14.7) have also had strong offensive seasons on the heels of Maine’s 11-7 record in the Showcase Cup.

“I expected this team to come in and score at a high clip, shoot at a high clip,” said point guard JD Davison, who had 14 points and eight assists Saturday. “During training camp, I saw a lot of shooters, a lot of scorers.”

The Celtics led the G League at 122.5 points per game entering Saturday, but they’ve struggled lately. A broken finger has sidelined Valentine, the team’s second-leading rebounder, for seven games, and Samanic has missed the last four in the Health and Safety Protocol.

“Those guys are obviously really good players with NBA experience, that have been really good for us all year,” Barlow said. “But at the same time, we always tell our guys the other 10 guys are also really good.”

Barlow wasn’t making excuses for a team that allowed 110.3 points per game in the seven wins but has allowed 123.3 over the last six games.

“We’ve got enough talent and enough good players to win,” he said. “We haven’t been quite as crisp defensively, transition defense hasn’t quite been as good. … Some of that’s schedule, and some of that’s we have to be better.”

The team isn’t worried.

“That’s just the way the season goes, there are going to be some ups and downs,” Smith said. “It’s a good opportunity for us to grow as a team. It can be beneficial to us later down the road.”

There’s reason for optimism. Valentine and Samanic are likely to return this week. In their absence, Baldwin and Shayok, who has scored 82 points over his last three games, have stepped up.

“I still wanted to be aggressive,” Shayok said. “The coaches try to put me in good positions to score, along with my teammates finding me. I think it’s been me being myself, and it’s showing on the court.”

The Celtics haven’t had to deal with the personnel puzzle they did last year. Maine was a revolving door and saw six players leave for NBA teams by mid-January. This season, the roster has remained intact.

“It makes the job a lot easier,” Barlow said. “Last year, we were just picking up guys straight off the plane to the huddle, picking up guys in the hotel lobby and giving them a jersey to play. It’s really hard having any consistency when you do that. It’s hard to get in a rhythm, hard to get guys used to playing with each other.”