The Galaxy's Gabriel Pec, center, scores against Minnesota United's Jefferson Diaz, left, and goalkeeper Dayne St. Clair during the first half Sunday in Los Angeles. (Etienne Laurent/The Associated Press)

Everyone knows that the way to win in the MLS playoffs is with defense and opportune finishing.

Nobody told the LA Galaxy, though. They’re just going to win by scoring tons of goals.

Minnesota United went into Sunday’s Western Conference semifinal in Los Angeles looking to use its top-notch defense to clamp down on the Galaxy’s star-studded attack. It’s accepted road-game wisdom: stop the other team, maybe steal a goal of your own and hope to keep the home team quiet.

Sunday, that hope lasted 28 seconds — and presaged the rest of the night, as the Loons went down to a 6-2 defeat.

“It’s frustrating, because all the things we kind of prepared for and spoke about where the dangers were, that’s where we didn’t manage those moments well enough,” Loons center back Michael Boxall said from Los Angeles.

All it took was one bad pass in the opening moments, and All-Star Galaxy midfielder Riqui Puig got loose, driving forward into space with the ball in exactly the way the Loons wanted to prevent. He fed an extraordinary long pass to star winger Gabriel Pec, who beat a defender and then goalkeeper Dayne St. Clair, giving the Galaxy the lead before the smoke from fans’ flares had even begun to dissipate.

It set the tone for the rest of the game, with the Galaxy repeatedly opening up the Loons defense and strolling in on goal. Los Angeles got two more goals before the first half was over. Dejan Joveljic scored from a Marco Reus free kick in the 18th minute, a too-easy header in which all the Galaxy center forward had to do was jump where he was standing and flick the ball in.

In the 37th minute, right back Miki Yamane sneaked forward, received a long pass from the LA back line and delivered a cross. Joveljic missed his kick, but Joseph Paintsil was at the back post to clean things up — a frustrating moment, since Yamane had been one of the Galaxy’s under-the-radar offensive weapons against the Loons earlier this season.

Amazingly, despite the deluge of goals, at halftime the Loons were still a goal away from parity. Kelvin Yeboah tied the score only five minutes in, blasting a powerful shot past a defender and goalkeeper John McCarthy, and he scored again just before the half ended on a penalty kick to pull his team within 3-2.

McCarthy actually saved Yeboah’s first penalty effort, but replay showed that the goalkeeper was off his goal line, and the kick was retaken. At his second attempt, Yeboah drove the ball into the side netting.

However, any hope of a turnaround in the second half was killed five minutes in, with Pec on the score sheet again. While the 23-year-old Brazilian had 16 goals in the regular season, few could have been as good as this one. It was all Pec, who picked up the ball 20 yards into his own half, then dribbled past three defenders on a straight line to the Minnesota goal, finishing inside the far post for a second time.

“We, of course, knew the level of threat that the forwards posed, but had every intention of this not being a game that was played in big open spaces,” said Loons coach Eric Ramsay, whose team had given up a total of two goals in its previous seven matches.

From there, the second half was almost all Galaxy. First, St. Clair saved a Pec penalty kick, but other than confirming his status as the king of penalties and preventing Pec from getting his hat trick, all it did was make the final score better.

Loons center back Jefferson Díaz was sent off with less than 10 minutes to go for a pair of second-half yellow cards — killing any hope of a comeback and opening the door for the Galaxy to pad to their total. Paintsil and Joveljic both added late goals, giving all three members of LA’s star-studded forward trio a pair of goals for the evening.

Los Angeles has scored four or more goals in all three of its 2024 playoff games. The Galaxy are the highest seed remaining in the MLS playoffs, meaning they have a chance to play two more games at home, where they haven’t lost all year.

The Loons, meanwhile, will have no more to do this season … except to figure out where their plan went wrong in Los Angeles.