Milwaukee ? Even before the first pitch, the Milwaukee Brewers took a swing at the St. Louis Cardinals.

Come Sunday, the Brewers swapped their barbs for bats — and just kept bashing.

Needing a comeback in the NL championship series opener, Milwaukee turned to its power duo of Ryan Braun and Prince Fielder, then got a clutch hit from Yuniesky Betancourt to beat the Cardinals, 9-6.

The Brewers celebrated wildly as the big hits came during a rapid-fire rally.

“It’s the playoffs, bro,” Fielder said. “You’ve got to let it all out.”

Braun launched a two-run, 463-foot homer in the first inning and added a two-run double during a six-run burst in the fifth. Fielder hit a two-run homer and the typically light-hitting Betancourt added a two-run homer to cap it.

The midgame turnaround came so fast that the crowd wasn’t done cheering Braun’s big hit when Fielder went deep.

“I don’t even know if I heard the ball come off Prince’s bat,” Brewers manager Ron Roenicke said. “I knew it was a good swing and came off nice, but when you can’t hear the ball, the sound of it, because of all the people yelling. I wasn’t sure what was going to happen there until I saw the ball flight.”

At least for one game, the bitter NL Central rivals avoided any on-field confrontations in their first postseason matchup since the 1982 World Series.

That’s despite an already tense atmosphere that gained some steam when Brewers starter Zack Greinke let it slip on Saturday that some of his teammates don’t like the Cardinals’ Chris Carpenter — a comment that drew a stern rebuke from Cardinals manager Tony La Russa.

Greinke hinted that he heard a few comments from the Cardinals’ dugout Sunday, but he said it was nothing out of the ordinary.

“They’re yelling from the dugout some, but most teams do that,” Greinke said. “Everyone always makes fun of me grunting when I throw a fastball. It’s kind of funny sometimes, but no big deal.”

The atmosphere was tense even before the first pitch, as La Russa was showered with boos during pregame introductions. He calmly tipped his cap to the crowd.

La Russa said afterward that he hoped the tension wouldn’t overshadow the competition — although he said he had a sense that some fans and media members would be disappointed if there aren’t any repeats of the on-field confrontations the teams have had in the recent past.

“I don’t want our players and their players to be egged on, and I don’t think they will,” La Russa said. “We’re going to play as hard and good against each other as we can.”

Greinke struggled at times, but reliever Takashi Saito got Cardinals star Albert Pujols to ground into a key double play in the seventh. Francisco Rodriguez pitched a hitless eighth and closer John Axford threw a hitless ninth for a save.

Game 2 is at Miller Park tonight. Shaun Marcum starts for the Brewers against Edwin Jackson.