As Lawrence’s boys basketball team struggled through a 4-13 campaign last season, Marquan Williams sat in the stands and observed.

He believed he could have an impact as a point guard on this year’s team, so he tried out and earned a starting role. But his effort has gone beyond making plays on the court. He espoused a role deeper than a fan last year. He was a keen observer, and he has surprised coach Lou Robinson with his memory of key moments that went awry.

“I’ll be like, ‘How do you know that?’” Robinson said “He’s like, ‘I was watching coach. I was paying attention.’ That’s really helped him this year.”

So Williams remembers how Valley Stream South swept Lawrence last year. “Oh, yes, I do,” he said.

On Tuesday night, he had an opportunity to return the favor. The senior converted both ends of a one-and-one to extend a one-point lead with 26.6 seconds left in Lawrence’s 46-45 Nassau A-III win over the visiting Falcons.

Hall Elisias (seven points, 16 rebounds, seven blocks) answered Williams’ foul shots with a layup with 6.6 seconds left, but the Falcons (6-6) did not have another opportunity to lock up a playoff berth as they seek to defend their Long Island title.

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“It’s nothing personal,” Williams said, but teammate Sammy Robinson disagreed.

“Revenge,” Robinson said. “That’s it.”

Williams had eight assists to go with his five points — the rest coming on a buzzer-beating three that gave Lawrence a 32-30 lead entering the fourth.

As Williams stepped to the foul line, Sammy Robinson (24 points, 10 rebounds and four steals) said he was thankful. The Golden Tornadoes (9-3) had seen a 44-37 lead shrink to 44-43 in 90 seconds, thanks to turnovers and ill-advised field-goal attempts early in the shot clock. Sammy Robinson had reason to believe Williams would not fold under pressure.

“He’s the man in practice who knocks them down whenever we need them so we don’t run suicides,” said Sammy Robinson, who scored 10 points in the fourth quarter.

Valley Stream North, which swept the season series with Lawrence, beat Floral Park Tuesday to improve to 10-2, so the Golden Tornadoes’ third one-point victory this season kept them alive for the conference title with two games remaining.

“We’re here to play basketball,” Williams said, “and to try to make it to the Long Island Championship and states.”