Johnston scored a goal on four shots and added six hits in Sunday's 2-1 win over the Golden Knights in Game 7.
Johnston capitalized on the Golden Knights botching a clearing attempt, taking the loose puck and scoring at 14:34 of the first period. The 20-year-old center finished the first round with four goals and three assists in seven contests, to go with 27 shots on net, 11 hits and an even plus-minus rating. He's played both as the third-line center and first-line right wing, giving the Stars a couple of roster constructions that work heading into the second round versus the Avalanche.