"He's been really steady for us and he plays a great all-around game," Popovich said.
Belinelli made his first two 3-pointers against the Pelicans after opening with a 15-foot jumper off an assist from Duncan.
Belinelli's first 3-pointer with 6 minutes remaining in the first quarter gave San Antonio a 16-4 lead. The Spurs would never lead by less than 10 points the rest of the way.
After Alexis Ajinca hit a 17-foot jumper on the game's opening possession, New Orleans did not score again until Greg Stiemsma's dunk with 8:21 remaining in the first quarter. The three-minute drought was followed by another three-minute drought.
"We couldn't finish in the paint tonight," Williams said. "We were 18 for 48 in the paint. That's a bad number for us. We're a team that usually is high when it comes to points in the paint."
Rivers' layup with 30.9 seconds pulled New Orleans within 69-59 with 30.9 seconds left in the third quarter, but Belinelli hit back-to-back 3s to fuel a 12-3 run and San Antonio reasserted its control.
San Antonio travels to Indiana to play the Eastern Conference-leading Pacers on Monday.
NOTES: Three-time Masters champion Phil Mickelson sat courtside during the game cheering the Spurs. Mickelson withdrew Saturday from the third round of the Valero Texas Open after injuring an oblique muscle. "I pulled a muscle on my downswing trying to hit the ball hard on the second hole (his 11th)," Mickelson said in a statement. "It just killed and it wouldn't subside for 10 or 12 seconds." ... Spurs W Danny Green (right foot inflammation) and Matt Bonner (right calf strain) both sat out the game. ... Roberts played 29 minutes after being listed as day to day with a left knee bone bruise.