They say defense wins championships, and who’s to argue?

In baseball, though, it goes a step further.

Bullpens win championships.

Which is why the Cubs acquired left-hander Aroldis Chapman for the ninth inning. Which is why manager Joe Maddon, during the Cubs’ 1-0 victory over the Giants in Game 1 of the NLDS, was prepared to stray from the conventional with his pitching staff now that the postseason has begun.

Maddon was allowed to play it straight, though, bringing in Chapman in the ninth after Javy Baez homered into the basket in the bottom of the eighth. Chapman was entering whether the Cubs took the lead or not, Maddon said.

This is why the Cubs got Chapman from the Yankees on July 25, for postseason moments like these. He struck out Gorkys Hernandez, retired pinch-hitter Eduardo Nunez on a grounder to second, and, after Buster Posey – who is 6-for-11 lifetime against Chapman — lined a double to the wall in left-center, retired Hunter Pence on a ground ball to second to end the game.

“I felt the emotion of the crowd,’’ Chapman said through a translator. “I love it because everywhere I go I hear about this team, and I just felt that emotion from the crowd. It gave me energy in the ninth inning. It was an incredible experience.’’

Maddon had Chapman ready in the eighth inning of a scoreless game and was prepared to call on him if the left-handed hitting Brandon Belt came up or if the Giants got something going against starter Jon Lester in the eighth.

“When you have a guy who throws 104, it’s his game to finish all day and every day,” Lester said.

That finish can begin in the eighth, Maddon said, especially in a best-of-five series “when you have five days to win three games” to move on to the next round.

“So, yeah, you have to be less tolerant,’’ said Maddon, who, in a conventional Cubs bullpen world, would have Pedro Strop as the seventh-inning guy and Hector Rondon the eighth-inning man.

For all the talk about lineups, Maddon said the thing he worries about most on a daily basis is the bullpen.

“Lineup construction is relatively easy,’’ he said. “When it comes down to how you’re going to manipulate your bullpen nightly and who is well and who are you pushing too far and who can handle what kind of moment, what’s the best matchup for them. That’s the biggest concern on a daily basis.”

“Your skills versus this group of hitters is much more important than whether it’s the seventh or eighth inning.’’