Seguin felt the Stars controlled the 5-on-5 play most of the game.
"It came down to special teams, honestly, and they won special teams," he said.
With Dallas defenseman Jamie Oleksiak in the penalty box for tripping, Galchenyuk made it 2-0 at 15:31 of the second.
"We spend so much time talking about the power play, and in the video room," Galchenyuk said. "We, as a group, are happy it paid off today."
Galchenyuk made it 3-0 at 3:39 of the third for his second multigoal game of the season. Ritchie scored with 3:39 left to make it 3-1, and Radulov scored with 3:12 remaining for the 3-2 final.
"You have to play 60 minutes, that's the bottom line," Radulov said. "It's not enough to play two periods or 50 minutes, it's a 60-minute game. We have to understand that, embrace it and be better."