"There's a saying that an NHL defenseman doesn't really define himself until about 250 or 300 games," Armstrong added. "He's around 160, so there's still some growth there, some definition going into his game, but he's got all the tools to be a very good player over time, and we're very excited to have him part of our group."
Last season, Parayko played in 81 regular season games, posting a career-high in points with 35 (four goals, 31 assists).
For his career, the 6-foot-6, 226-pound defenseman has collected 68 points (13 goals and 55 assists) and a plus-35 rating in 160 regular season games.
"I think we knew we had a special player with what we saw last year," Armstrong said of Parayko's rookie season. "The World Cup of Hockey brought him more national attention…and the World Championships, he went over there and became a big player for Team Canada immediately. It shows that in his age bracket, he's one of the better players."
In 31 playoff appearances, Parayko has four goals, eight assists and a plus-7 rating.
A native of St. Albert, Alberta, Parayko was originally drafted by the Blues in the third round (86th overall) in 2012.
"Playing in St. Louis, in front of all those fans who support us on and off the ice - there's no better place to be."