The Leafs got 26 saves from Frederik Andersen, who returned to the crease after watching his team blow a 4-1 third-period lead in Saturday’s 6-5 shootout loss to the Montreal Canadiens in the second game of a back-to-back.
The visitors snapped a 2-2 deadlock at 7:51 of the third when David Perron found a pinching Pietrangelo, who beat a down-and-out Andersen from a tight angle at the bottom of the faceoff circle.
The goal was the second of the season for the Blues captain, the 400th point of his career and his 23rd game-winner to break a tie with Al MacInnis for the most by a defenceman in franchise history.
St. Louis had a chance to put the game away when Toronto defenceman Jake Muzzin went off for slashing with 4:57 left in regulation, but the Leafs had the best chance when Binnington robbed Ilya Mikheyev with his right pad off the rush.
Toronto pressed with Andersen on the bench for the extra attacker, but couldn’t find a way past Binnington and the Blues’ stout, battle-tested defence.
The Blues opened the scoring at 8:30 of the second when Sundqvist — the Blues’ fourth-line centre — moved in on Andersen and blasted a slapshot from the top of the faceoff circle that the Toronto netminder will want back.
The Leafs responded with a spirited fourth-line shift of their own to tie the score when Jason Spezza batted a puck out of the air to Gauthier, who banged home his second of the season at 11:34.
A healthy scratch for two of Toronto’s first three games, Spezza suited up at home for the first time in blue and white, and also registered his first point with the Leafs after signing for the league minimum in free agency on July 1.
Fans at Scotiabank barely had a chance to sit back down when they were on their feet again 24 seconds later when Nylander finished off a beautiful passing play with Cody Ceci and Andreas Johnsson for his second.
Following a long contract impasse that dragged into December, it took Nylander until his 24th game to score his second goal of the 2018-19 campaign.
But the Blues, who went from last in the overall standings in January to winning the franchise’s first Stanley Cup in June, pushed back late in the period and got the equalizer with 47.3 seconds left on the clock when Schenn beat Andersen between the pads after Toronto defenceman Morgan Rielly turned the puck over.
A native of nearby Richmond Hill, Ont., Binnington made his first-ever start at Scotiabank Arena after not grabbing the No. 1 job in St. Louis until early January of last season.
The 26-year-old, who did beat the Leafs 3-2 in overtime at Enterprise Center on Feb. 19, was helped out by two posts in a busy first period.
Toronto centre Alexander Kerfoot found iron just two minutes in after moving in alone on Binnington. Andersen snapped his glove out at the other end to deny Schenn after the Leafs were caught running around in the defensive zone for an extended period.
Auston Matthews, who came in five goals in three games to open the campaign, then rang another shot off the post behind Binnington on a Toronto power play before Nylander couldn’t quite control a loose puck with the St. Louis netminder down and out.
Notes: Toronto hosts the Tampa Bay Lightning on Thursday, while St. Louis visits the Ottawa Senators the same night. … Attendance was 19,466.