ST. LOUIS — He is the youngest player on either roster in the Western Conference finals, but Blues rookie Robert Thomas is playing well beyond his age.

Thomas, who won't turn 20 until July 2, showed off the offensive skill and speed against Dallas that led St. Louis to make him the 20th overall pick in the 2017 entry draft.

One goal and four assists might seem modest, but Thomas' speed and chemistry with linemates Pat Maroon and Tyler Bozak helped the Blues advance to their first conference final since 1996 and just their fourth since 1970. His plus-5 play in the post-season is second-highest on the team.

Thomas assisted on both goals in their 2-1 win over the Stars in Game 7.

"He had a really good game," Blues coach Craig Berube said. "From the get-go, he had the puck and he was doing some real good stuff with it."

With his assist on Maroon's game-winner in double-overtime, the Canadian became just the second rookie in franchise history to figure in a series-clinching overtime goal. Doug Gilmore did it against Detroit in 1984. Thomas also became just the second teen in NHL history to factor into such a goal, joining Boston's Bep Guidolin, who was 17 when he did it in 1943.

He wasn't nervous and it showed.

"No, once you get out there it's like every other game," Thomas said. "Obviously, the pressure is a lot, but you have to stay composed and really just focus on the game."

Thomas wasn't guaranteed a spot on the roster when the team began training camp in September. He struggled at times in the regular season, but finished with nine goals and 24 assists in 70 games. He improved as the season went on.

"I think it just took time for him to get settled in here in the NHL and find a comfort zone for him and I'm not sure exactly when it clicked in," coach Craig Berube said. "From the get go you could see the skill and talent he has. It just took a while to get up to speed. The NHL is a lot faster than junior and things are done quicker and harder and all that. He's obviously a very smart player and got acclimated pretty quick."

Meshing with Maroon and Bozak was perhaps the most important development.

"With Thomas, just unbelievable skill," Maroon said. "His hands in tight, it's like stick handling in a phone booth. The guy can do a lot of good things. He drives the bus on the team. He's got young legs, good skill and sees the ice so well. He's probably one of the best players on our team on top and below the circles, how he can cut back and turn and how he can make plays in tight areas."

The line is a bit of a variety show: The skilled Thomas, Bozak a top faceoff man and Maroon a big body who goes to the net. On the game-winner against Dallas, Bozak won the faceoff, Thomas used this speed to cut back, circle and create space for himself to release a shot that clanged off the post and deflected off the back of Stars goalie Ben Bishop. Maroon was there to clean up the rebound.

"I knew it was a big game, so I had to step up and really make my mark on the game," Thomas said. "As a line, we've been saying this all series. That when the time comes, we've really got to be the line that steps up and we've got to create the chances."

Thomas' play was so strong in Game 7 that Berube double-shifted him at times. He finished with 22 minutes, 50 seconds of time on the ice, a career high by almost four minutes.

The rookie has been living this season with former Blues star Keith Tkachuk as he gets settled in as a NHL player. Both of Tkachuk's sons play in the NHL, Matthew for Calgary and Brady for Ottawa. Both sons have returned home with their respective teams' seasons over so the Tkachuk household is pretty full.

Thomas, who was a teammate of Matthew with London in the Ontario Hockey League, now has some added clout with is standout play.

"Oh yeah, I don't think they can boss me around anymore," Thomas said. "That's great."

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Joe Harris, The Associated Press