The Spurs steadily pulled away from the Clippers to build a 2-0 lead in the Western Conference semifinals after sweeping Utah in the opening round.
The series moves to Los Angeles for the next two games Saturday and Sunday.
San Antonio, seeded No. 1 in the West, scored at least 100 points for the fifth time in its six post-season contests. The Spurs shot 53 percent from the field and limited the Clippers to three offensive rebounds.
Tony Parker led the Spurs in scoring with 22 points, but it was Duncan and Diaw who provided the consistent spark that prevented the Clippers from putting together a run.
Diaw made all seven of his field goal attempts while scoring 16 points and Duncan went 9-of-14 for 18 points. Danny Green added 13 for the Spurs and Manu Ginobili had 10.
San Antonio began to put the game away with a 13-4 run early in the third period that gave the Spurs a 65-51 cushion.
Blake Griffin had 20 points for the Clippers, but no other Los Angeles player scored more than 11.