Riikola scored his second NHL goal on the power play at 4:58 of the second period to tie it 1-1.
"He can really shoot the puck. That's something we recognized in training camp, early on, he can really shoot the puck," Penguins coach Mike Sullivan said of Riikola, a rookie defenseman.
Pittsburgh outshot Arizona 13-4 in the second.
"The second period, I think, was one of the best periods we played all year," Murray said.
Guentzel put the Penguins ahead 2-1 at 5:38 when he scored from along the goal line off the rebound of his own backhand shot.
"[Kuemper] made a good save, and I was just trying to throw it on net. I knew it was a bad angle, I don't know if it hit anything or not," said Guentzel, whose 24 goals lead Pittsburgh. "It was nice to get one."
Panik appeared to tie the game when he scored at 3:41 of the third period, but Sullivan challenged for goalie interference by Ekman-Larsson, and the goal was overturned after video review.