The Stanley Cup champion Blues, meanwhile, served notice they are fast becoming a hot mess in return-to-play competition.
Stecher broke a 2-2 tie in the third period when he raced down the right wing and wired a slapshot from the face-off circle under the arm of St. Louis goalie Jordan Binnington.
Stecher then pointed to the sky afterward to acknowledge his father, Peter, who passed away on Father’s Day due to complications from diabetes.
“It’s been tough obviously at certain moments throughout this process,” said Stecher, 26.
“I had a couple of seconds there to reflect on my dad. The biggest thing was everybody showed their support on the bench instantly, kind of gave me a tap, and that kind of motivated me to keep it going.”
Teammate Elias Pettersson embraced him on the bench.
“What Troy had to go through during the summer, I just wanted to go and hug him,” said Pettersson.
Captain Bo Horvat scored twice for the Canucks, who are making their first playoff appearance since 2015.
Pettersson and J.T. Miller also tallied for Vancouver while David Perron and Jaden Schwartz replied for St. Louis.
The Canucks got scoring up and down the lineup to beat the Minnesota Wild three games to one in qualifying play, and that balanced attack continued against St. Louis, with Stecher getting his first of the post-season.
Rookie defenceman Quinn Hughes, a Calder Trophy finalist, added an assist to give him a goal and six helpers in five games. Goalie Jacob Markstrom made 29 stops for the win.
Horvat said they were ready to match the Blues intensity.
“They won the cup for a reason, so we were ready for it,” said Horvat.
“I thought we showed some good things tonight, some pushback and obviously scoring those big goals late was a huge clutch for us,” he said.
“And I couldn’t be happier for Troy to get that one. I think I can speak for everybody (on that).”
Vancouver never trailed in the game
The teams swapped mirror-image power-play goals in the first period.
Horvat opened the scoring when he one-timed a Hughes’ feed from the top of the left face-off circle past Binnington. St. Louis matched that when Perron half-slapped a pass from Brayden Schenn from the top of the right circle high over the glove of Markstrom.
Vancouver regained the lead on the power play midway through the second period. Pettersson whipped the puck under the bar off a goalmouth scramble. The Blues replied when Schwartz tipped the puck past pinching Canuck defenceman Chris Tanev at the Blues blue line, then barrelled in on a breakaway and beat Markstrom with a nifty backhander through the five hole.
After Stecher made it 3-2 in the third, Horvat, entering the Blues zone with speed, turned Blues defenceman Vince Dunn inside out, raced in and fired a wrist shot past Binnington on the blocker side. Miller scored on the power play with less than 40 seconds to play.
Binnington stopped 17 of 22 shots to take the loss.
The Canucks are winning with a mix of veterans and playoff newbies.
Pettersson, Brock Boeser, Jake Virtanen, Tyler Motte, Hughes, Stecher, Zack MacEwen, and Markstrom were regulars playing in their first playoff game (although technically they have playoff experience as the qualifying round statistics will count as post-season ones).
The loss continues the Blues’ return-to-play downward spiral.
St. Louis was the best in the Western Conference (42-19-10) and second overall in the league when the NHL suspended play March 12 due to the COVID-19 pandemic.
But they blew third-period leads in every game against the other three top teams in the round robin, going winless while scoring just six goals in three contests to drop from the top seed to the fourth.
St. Louis head coach Craig Berube said he saw positives against Vancouver.
“I thought that we did a good job controlling the tempo and the play,” said Berube.
“We had a lot of good looks. We’re going to have to do a better job of getting more traffic in front of their goalie and getting some greasy goals.
“Listen, we’ll fix it. We’ll get better next game. It’s a long series.”
History is on Vancouver’s side. The teams have met three times in the playoffs (1995, 2003 and 2009). Each time the Canucks bounced the Blues out in the first round.
The Western Conference games are being played at Rogers Place, with all players being kept in isolation to avoid contracting COVID-19.