BOSTON — Mark Anthoine loves his big games.

In his first game at TD Garden, on the biggest stage on which he’s yet played, the Lewiston native played hero for the University of Maine.

Anthoine swiped the puck in the Boston University zone with his team on the power play, curled to the center of the slot, looked to pass to a defender and then fired wrister high glove past BU keeper Kieran Millan at 7:43 of the third period to lift the Black Bears to a 5-3 victory over the Terriers in the teams’ Hockey East semifinal.

“I guess I like big stages, I don’t know,” Anthoine said. “It’s just, you go through stages where you don’t necessarily play as well as you want to, and then you get one, or an assist, and it just snowballs.”

Anthoine’s goal developed seemingly from nothing.

“(Brian) Flynn had picked it up on the half wall and fired it to the net with Joey Diamond out front,” Anthoine said. “I think it was (BU defenseman Adam) Clendening, and I just got all stick on it. I was looking to pass to someone, and no one was really around. Joey had the screen and I shot it.”

“That’s the ‘shooting is always the last resort,’ mentality,” Maine coach Tim Whitehead interjected, drawing laughter from the crowd. “There were three of us coaches yelling, ‘Shoot.'”

It was a shining moment for Anthoine, playing in his first game on Garden ice after skating on the Boston Bruins’ home sheet for the first time in a Thursday practice.

According to Whitehead, Anthoine’s goal is yet another step in his impressive development.

“That was a pretty quick release for someone thinking pass,” Whitehead said. “There’s a guy there, what an improvement. A lot of people talk about (Matt) Mangene, and how far he’s come, but you look at Anthoine, he’s got 10 or 11 power-play goals for a guy who had one or two goals last year. We’re really proud of Mark and his development. He’s been scoring big goals, too. He had the two at Fenway, and then the game-winner (Friday).”

The power-play goal was the Black Bears’ third with an extra skater Friday. They finished 4-for-6.

“We just kept it simple, and sometimes they go in, sometimes they don’t,” Whitehead said.

Maine withstood a brief flurry of activity in its own end in the final 1:45 as BU pulled Millan (39 saves) for an extra skater, but earned a late power play after Clendening hauled Matt Mangene to prevent an empty-net goal. After another big flurry and several big stops by Maine goalie Dan Sullivan, Diamond scored into the empty net with 28.7 seconds remaining — his second of the game — to seal the victory.

Will O’Neill, known for his solid defense and play-making ability from the point — particularly on the power play — doubled his season-long goal output in one night, marking a pair of goals Friday, his second and third of the season.

BU had knotted the contest at 4:03 of the third on a virtual power play. A hit to Maine’s top player and leading Division I scorer Spencer Abbott — a replay appeared to show Abbott taking an elbow to the head — left the Maine assistant captain immobilized behind Millan. He remained on the ice writhing in pain, but the Terriers maintained control of the puck, so officials could not blow the play dead. On the rush, which turned into a 4-on-3, Matt Nieto and Clendening worked the weave well and Nieto beat Sullivan with a deke to the forehand.

Abbott appeared next to the Maine bench later in the third in a suit and tie.

“He’s obviously a tremendous player, and whenever anybody like that goes down, everybody else has to step up,” Whitehead said. “I think that’s what we did.”

BU got the start it wanted, but couldn’t maintain any consistent pressure.

“We had a lot of key guys just disappear tonight,” BU coach Jack Parker said. “We looked jumpy as heck, we looked like we were afraid to lose, trying not to lose instead of trying to win from the get go. It was a bad frame of mind from the get go.”

Alex Chiasson opened the scoring just 2:46 into the game to put the Terriers on top 1-0.

The Black Bears went on their second power play with 10 seconds remaining in the first on a slashing call to BU’s Sahir Gill. This time, they made it count. Forty-six seconds into the second frame, Diamond fired the puck past Millan as a BU defender knocked his own keeper over, knotting the game at 1-1.

BU went back in front at 6:16 with its own power-play goal only eight seconds into the man advantage, but the Black Bears clawed back again with the equalizer at 11:22 as O’Neill’s first snuck through a screen less than a minute after Maine had a goal waved off after the puck struck the post. O’Neill’s second, on the power play at 18:25, put Maine in front for the first time late in the second.

“They have a great power play, there’s no question,” Parker said. “But they got power-play goals that were like, ‘How did that happen?’ We passed it to them, or we turned it over and gave them a 4-on-2. We ran our own goalie. So it wasn’t a very good night for us, and it was a real good game for them.”

Maine faces Boston College in the Hockey East final Saturday at 8 p.m. at the Garden in a rematch of the 2010 Hockey East final, which BC won, 7-6.