Nick Schmaltz had two goals and an assist, and Mikhail Sergachev and Clayton Keller each had a goal and two assists for the Mammoth (19-19-3), who had lose two straight. Karel Vejmelka, who returned after missing the past two games with an upper-body injury, made 20 saves.
Calum Ritchie and Matthew Schaefer scored, and Maxim Shabanov recorded two assists for the Islanders (22-15-4), who have lost two of three (0-2-1). David Rittich was pulled in the third period after allowing five goals on 14 shots. Marcus Hogberg made four saves in relief in his first appearance of the season.
Guenther gave the Mammoth a 1-0 lead 36 seconds into the second period when his wrist shot from inside the left face-off circle banked off Rittich’s helmet and in.
Ritchie tied the game 1-1 after he beat Vejmelka glove side off the rush at 2:35 of the second.
Guenther scored his second of the game to make it 2-2 at 10:20 of the second after he one-timed a Lawson Crouse pass from the slot high glove side.
Schmaltz extended the lead to 3-1 at 16:19. Tony DeAngelo couldn’t corral a puck at the Utah blue line before Schmaltz beat Rittich high glove side off a 2-on-1 rush with Keller.
Sergachev gave Utah a 4-1 lead with a power-play goal at 2:52 of the third when his point shot beat Rittich low glove side.
Keller scored a power-play goal at 5:41 of the third period to give Utah a 5-1 lead with Rittich caught out of position.
Schaefer scored on the power play at 11:48 of the third to cut the deficit to 5-2. He beat Vejmelka low glove side from the point, becoming the youngest defenseman in NHL history to reach 10 goals.
Guenther completed his hat trick and made it 6-2 at 13:54 of the third. He beat Hogberg through the legs off the rush from inside the left circle.
Schmaltz scored his second of the game at 16:55 of the third, beating Hogberg glove side from the low slot off a feed from J.J. Peterka to make it 7-2.
Islanders forward Bo Horvat left the game midway through the third with an apparent lower-body injury after getting tangled with Mammoth defenseman Sean Durzi at the red line and did not return. Horvat was named to Team Canada for the Olympic Winter Games Milano Cortina 2026 on Wednesday.
