MONTREAL — Three minutes and nine seconds—that's how long it took for Lassi Lappalainen to bring thousands of Impact fans to their feet.

Lappalainen scored twice in his Major League Soccer debut to lead Montreal (10-11-3) to a commanding 4-0 victory over the first-place Philadelphia Union (11-7-6) on Saturday night.

The Finnish winger scored in the fourth and 46th minute of play as the Impact snapped a four-game losing skid in league play with their biggest win of the season.

"I had a dream where I scored one goal," said Lappalainen, who joined Montreal this week on loan from Bologna. "So it wasn't like in my dreams. But this is a dream now.

"My first goal gave me confidence. It just really helped me play the rest of the game. The goal was so relieving."

Orji Okwonkwo also scored twice for Montreal while Evan Bush made three saves for his seventh clean sheet of the season. It was Montreal's first-ever 4-0 victory since joining MLS in 2012.

Lappalainen was one of the best players on the pitch. He beat his opponents with speed and fancy footwork and even showed off his defensive abilities.

In the fourth minute of play, the speedy midfielder made a run into the box behind a Philly defender and snagged Zachary Brault-Guillard's perfectly weighted through ball. Lappalainen's first touch evaded goalkeeper Andre Blake, and his second touch was an easy tap-in into the back of the net.

The entire Impact team swarmed the Finnish international at the corner flag to celebrate.

Just 16 seconds into the second half, Lappalainen netted his second of the match to give Montreal a 3-0 lead. The 20-year-old blew past the Philly defence, walked into the box and placed a side-footed shot into the bottom far corner of the net.

"He showed off his speed and skill tonight," said coach Remi Garde of Lappalainen. "He showed a lot of maturity too. I am without reproach. It was extremely encouraging. He really set the bar high tonight. We're so pleased with his potential."

The Impact were winless since June 26 and had only scored four goals on their four-game slide. But they managed to put four past Blake in captain Ignacio Piatti's first MLS game since May 24.

After Lappalainen's opener, the Union pressed hard for the equalizer, looking to take advantage of Montreal's absent defenders Bacary Sagna (one-game suspension) and Victor Cabrera (arm injury).

Bush came up big in the 34th minute when he stopped Alejandro Bedoya's header off a corner kick. The Impact goalkeeper stood tall again on the very next play, denying Polish striker Kacper Przybylko from 12 yards out.

"Evan made two big saves that kept us in the game," said Garde. "That was a difficult moment for us. I'm happy for him because I know he's working hard. One more clean sheet is important for everyone, especially at home."

Those saves were crucial because Montreal doubled its lead, against the run of play, in the 36th minute. Piatti fed Okwonkwo with a through ball at the edge of the box and the Nigerian fired off the post and in for his fifth of the season.

With the Union playing a high line, a back kick by Maximiliano Urruti in the 66th minute sent Okwonkwo in all alone on goal with no Philadelphia defender nearby. The winger made it 4-0 with a low shot from near the penalty spot.

Union lost for the second time in three matches.

"A lot of their goals came from nothing," said Union defender Matt Real, who made his first start of the season. "It was just a night where everyone could have done better, including myself. Not much we can say about tonight. Everyone knows it was a flat performance."

The last time Montreal scored four times was in a 4-1 win against the Union on Sept. 15, 2018.

Notes: Lappalainen left the game in the 82nd minute to a standing ovation. … Montreal is 7-2-1 all-time against the Union at home.