Wyatt Johnston and Thomas Harley scored, and Jamie Benn had two assists for the Stars (32-14-9), who have won four in a row. Casey DeSmith made 12 saves.
Kailer Yamamoto scored twice for the second straight game, and JJ Peterka had two assists for the Mammoth (28-23-4), who have lost two straight and three of their past four games. Karel Vejmelka made 28 saves.
Harley opened the scoring while on the power play at 2:11 of the first period. Mavrik Bourque sent a wrist shot on net that hit off the left post and Harley put the rebound in past Vejmelka’s right pad from the slot.
Johnston extended the lead to 2-0 with a power-play goal at 7:42 when he set up in front and redirected Mikko Rantanen’s one-timer from the blue line.
Yamamoto cut the deficit to 2-1 at 10:23. Peterka rushed into the offensive zone down the left boards and fed a pass to Yamamoto, who sent a low wrist shot past DeSmith’s right skate from slot. Dallas challenged for goaltender interference, but the goal was upheld after video review. Peterka’s assist was his 100th in the NHL.
Duchene pushed the lead to 3-1 at 16:37 with a snap shot from the high slot that caught a piece of Vejmelka’s glove.
Yamamoto brought Utah to within 3-2 at 6:41 of the third period when his shot from the right circle fluttered past DeSmith on the glove side.