On a team that has a clearly defined Big Three, Omar Baxter has played in the shadows for Valley Stream North.

Baxter makes open jumpers. He finishes at the rim. He asserts himself on defense, boxes out, grabs rebounds.

“He does the little things that nobody notices on the court,” coach Dan Achatz said.

No more.

Everyone in Valley Stream North’s packed gym noticed Baxter on Thursday night.

The guard caught a pass from Taliq Abdul-Rahim and sank a buzzer-beating jumper from the foul line to lift the No. 3 Spartans over No. 6 Garden City, 55-53, in a Nassau Class A quarterfinal.

Valley Stream North (17-3) will face No. 2 Elmont Wednesday at Hofstra.

“It feels great,” said Baxter, who scored five points. “I’m glad to move on in the playoffs. That’s all I care about.”

Noah Shy (21 points), Josh Dennis (12) and Abdul-Rahim (11) — the team’s top three scorers this year — carried the offense throughout the game, but the Spartans never led by more than four.

Joe Leighton (26 points) and Andrew DeSantis (25) propelled Garden City to an 18-9 lead. After Dennis’ three-point play gave the Spartans a 45-41 lead at the end of the third, Leighton started the fourth with a three-pointer. He followed with a jumper and assisted DeSantis’ layup with 6:10 left to take a 48-47 lead.

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Jordan James’ two foul shots 55 seconds later put Valley Stream North ahead, 49-48. Shy, who had sat for nearly seven minutes with four fouls, returned and promptly sank a left-corner three with 3:37 left to expand the advantage to four.

“We had 10 seconds on the shot clock,” Shy said. “In my mind I was just shooting it.”

Leighton answered with another three, off a feed from Kevin McNiff, and his pump fake coaxed Dennis into the air, setting up a clean look from deep that would have given Garden City a two-point lead with 25.4 remaining. The shot rimmed out.

After Shy split two free throws with 16.9 seconds left, DeSantis dribbled down court in a hurry for a game-tying layup eight seconds later.

Achatz had one timeout remaining, but he chose to let Abdul-Rahim create.

“He made the correct pass,” Achatz said, “and Omar hit that shot at the free-throw line. He deserves it. The kid battles every day.”