Garnett also grabbed 12 rebounds while Avery Bradley and Brandon Bass each scored 18 points for the Celtics, who hold the fourth seed in the Eastern Conference.
They came into the contest trailing third-seeded Indiana by 2 1/2 games and with the win moved 3 1/2 games ahead of New York and Philadelphia in the Atlantic Division.
The Nets were led by Gerald Green's 15 points.
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