Marco Belinelli totaled 16 points, 11 rebounds and eight assists as the Spurs improved to 4-2 on their nine-game road swing.
Boris Diaw helped out with 18 points and Patty Mills added 16 for Southwest Division-leading San Antonio.
Rajon Rondo netted 16 points for the Celtics, which lost for the second time in six games heading into the all-star break.
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