MILWAUKEE — Left-handed hitter Michael Busch had just fallen behind in the count with the bases loaded in the second inning. The second strike was a curveball off the plate, but the call didn’t go his way.

Brewers right-hander Quinn Priester went back to a similar spot with the same pitch. And Busch wasn’t taking any chances. He stayed behind it and lifted it beyond the left-field fence for his first career grand slam.

“I’ll probably give [the ball] to my dad,” Busch said after the Cubs’ 10-0 victory -Friday. “He takes a little better care of it than I do — and that’s saying a lot.”

That blast turned what was already a tone-setting inning into an absolute gut punch to their division rivals. The Cubs took an eight-run lead and controlled the game from there.

With the highest run-scoring offense in the majors to begin the season, it has been easy for Busch’s contributions to fly under the radar — with the exception of a red-hot West Coast trip in which he homered in three consecutive games and had a would-be grand slam robbed by Dodgers outfielder Andy Pages.

Even on Friday, Busch shared the spotlight with Pete Crow-Armstrong, who had his second multihomer game of the season. He has hit eight home runs in the last 16 games.

“There’s a consistency to it that almost makes you not realize how good [Busch] is,” manager Craig Counsell said before the game. “And he’s got some streakiness in the home-run category. But he’s just been a consistent offensive player, so it’s pretty steady.”

Busch went on such a tear in Los Angeles and San Diego that when he was walking in from taking pregame ground balls at Petco Park, president of baseball operations Jed Hoyer called him the “king of the West Coast.”

Busch responded: “We’ve still got two games left.”

It wasn’t just a humble quip.

“Baseball is an amazing game, but sometimes it can kick you in the butt,” Busch said in a conversation with the Sun-Times last month. “And you just try to ride that time out, try to just be as consistent as possible. I walked into the season just wanting to be a little more consistent than I was last year. Which ultimately is tough to do in this game, but it’s a key component of why a lot of guys are really good and have been really good for a long time.”

Busch has tried to be diligent in his routine, regardless of results.

“Trying to flush yesterday, no matter if it’s good, no matter if it’s bad,” he said. “As hard as it is sometimes to do, I think just being aware of it has been pretty key for me so far.”

His grand slam Friday brought his OPS to .894.

The Cubs got their offense rolling against left-handed opener Tyler Alexander and Priester, pulling out to a 2-0 lead. But they turned up the heat in a seven-run second that featured Busch’s opposite-field power.

“I saw it in his early work today,” said Crow-Armstrong, who hit his first homer in that second inning. “I was out there with him, and he was just taking beautiful swings that way. That’s his [third] backside homer, too. And it’s not an easy place to do it here. . . . Glad he got that grand slam. He deserved it.”

Starting pitcher Ben Brown threw six scoreless innings, limiting the Brewers to four hits. Right-hander Chris Flexen relieved him, tossing three innings of one-hit ball in his Cubs debut.