Gerald Wallace and Brook Lopez each scored 15 for the Nets, who committed 20 turnovers and shot just 40.6 percent from the floor -- after shooting 56.3 percent in the first quarter -- to fall to 3-9 in December.
The Celtics scored 25 points of Brooklyn turnovers.
Brooklyn forward Kris Humphries missed the game due to an abdominal strain and will also sit out Wednesday's game at Milwaukee.
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