Neal Pionk had a goal and an assist for Winnipeg (2-2-0), which was coming off a 4-3 overtime win at the Colorado Avalanche on Wednesday. David Rittich made 27 saves in his season debut.
"We weren't really ready to go, obviously," Jets assistant coach Scott Arniel said. "Really sloppy hockey. We didn't execute in any area. We were turning pucks over. … Lesson learned. This league is a tough league, and if you don't come prepared to play, those things will happen."
Eichel made it 1-0 at 4:23 of the first period when he took a pass from Reilly Smith on a 3-on-1 and shot glove side from the slot.
"It's 3-on-1, so a lot of times you think, 'Well, we're going to score,' but it doesn't always work out that way," Cassidy said. "I like that it was one simple play. 'Smithy' freezes the D, gets it into the middle of the ice, and it's on net in a hurry."
Karlsson extended the lead to 2-0 at 6:11, scoring on a one-timer after receiving a backhand pass from behind the net by Michael Amadio.
Chandler Stephenson then made it 3-0 at 10:07 when his centering pass deflected in off Brenden Dillon's skate.
"I did not intend to do that. It was a lucky bounce," Stephenson said. "Usually, you got to get lucky to get something going."
Eichel pushed the lead to 4-0 at 15:17 of the first after he intercepted an errant pass from Rittich.