Logan O'Connor, Nazem Kadri and Gabriel Landeskog also scored as the Avalanche bounced back from a 4-1 loss at home two nights earlier, and improved to 3-0 on the road in the postseason.
"Of course it was a good answer from the last game," Lehkonen said. "We still know that we can clean up some stuff in our game and we've got to move on to the next one."
"I think there was a little bit of a momentum swing there," O'Connor said about the Blues changing goaltenders. "I think even before that we felt our game coming a little more. We weathered it early. They were hard on us to begin with, really closing down in the defensive zone.