Utah coach Kevin Colley said one of his lines wasn't prepared to come onto the ice, which eventually led to the vital defensive breakdown.
"We had some guys that were on Mars," he said, "and they need to come back down to reality and be good teammates and be alert on the bench."
Thunder center Justin Maylan capitalized on the loose puck in front of the Grizzlies' net with 3:03 in the second, rifling a wrist shot past the outreached glove of Engelage to score the first goal of the game. Fifty-four seconds later, Stockton wing Matt Bergland scooped up another loose puck, punishing the suddenly sloppy Utah defense.
"To be honest, it was just two good bounces for them," Engelage said, who had 30 saves.
While the Utah defense proved to be its ultimate undoing in its first game of 2013, the offense missed several golden opportunities.
Aside from Mitch Wahl's third-period power-play goal at the 15:53 mark, Utah couldn't find the back of the net.
Following Bergland's goal late in the second period, Grizzly forward Colin Vock couldn't capitalize on a opportunity, pushing a close shot wide.
While the Stockton defense did a valiant job of stifling the Utah offense, it was Thunder keeper Cody Reichard who was the star, stopping 26 Grizzly shots.
"You look at them in the standings and they're up there for a reason," Colley said. "I thought their goalie was their best player."
Utah now hits the road for a three-game set, which starts Friday in Ontario, Calif., followed by a two-game series in Las Vegas on Saturday and Sunday.
O A 2-1 loss ends Utah's six-game unbeaten streak.
• Stockton scores both of its goals in a one-minute span late in the second period.
• Utah forward Mitch Wahl scores the lone Grizzly goal on a power play early in the third period.
• Grizzlies head out on a three-game road trip, starting in Ontario, Calif., on Friday.