marc.carig@newsday.com

SAN FRANCISCO — Before Game 2 of the National League Division Series on Saturday night, Madison Bumgarner lugged his bat into the cage. He took his hacks with the same determination that he brings to the pitcher’s mound.

Over and over, the hulking Giants ace unleashed mammoth swings, taking aim at Waveland Avenue. At least once, he reached his destination. Later, when his team needed a pinch hitter, Giants manager Bruce Bochy did not hesitate to summon Bumgarner.

Bartolo Colon aside, pitchers’ at-bats in National League games often go overlooked. In recent years, a movement has grown to adopt the designated hitter, doing away with the mostly futile exercise entirely.

But Game 3 of the NLDS on Monday night featured a matchup of two of the game’s best-hitting pitchers in Bumgarner and Cubs righthander Jake Arrieta.

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And indeed, Arrieta hit a three-run homer on a 1-and-2 pitch from Bumgarner with two outs in the top of the second inning to give the Cubs a 3-0 lead. That gave Cubs pitchers three RBIs in each of the last two NLDS games.

“There’s a lot of time and energy put into that just to help carry our weight,” said Arrieta, whose .262/.304/.415 slash line this season gave the Cubs a bonus bat on days he pitched. “Being able to handle the bat can really put a lot of pressure on the other side.”

Of course, Bumgarner has long been one of the NL’s best- hitting pitchers. He had a .186/.268/.360 slash line this season, more than respectable for a pitcher. He also hit three homers — including one off the Mets’ Jacob deGrom — bringing his career total to 14.

“He’s one of the guys that you treat like a typical position player,” Arrieta said of Bumgarner. “You just have to approach him like you would any of their eight guys in the lineup. Try and mix things up and obviously try and neutralize his power because he’s a guy that can leave the ballpark at any time. So I feel like we’ll attack each other accordingly and not take it lightly.”

Still, the main event took place on the mound Monday night.

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Bumgarner went 15-9 with a 2.74 ERA in 34 starts, but he has been defined by his postseason brilliance. It was his four-hit shutout in Wednesday night’s wild-card game at Citi Field that sent the Mets packing. Arrieta went 18-8 with a 3.10 ERA one season after winning the Cy Young Award.

If Game 2 proved anything, in tense playoff games in which runs are at a premium, teams will take contributions from everywhere. And that includes from their pitchers.

In the Cubs’ 5-2 victory on Saturday night, Kyle Hendricks’ broken-bat single to centerfield drove in two runs and reliever Travis Wood — himself an accomplished hitter — became the third Cubs pitcher in history to homer in a postseason game.

To Arrieta, that success was no accident. During road games, he said Cubs pitchers often will congregate in the indoor batting cages when the position players are on the field. And at home, he said pitchers frequently get their swings in on the field.

In Chicago, helping one’s cause is taken seriously. “The mindset for us is we don’t want to go up to the plate and just be a free out,” Arrieta said. “That’s why we put so much time into it.”

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Ultimately, that work is part of the reason that the Cubs brought a 2-0 lead in the best-of-five series into Monday night’s game. It’s also why Bumgarner said he wouldn’t be letting up when Arrieta digs into the box — but Arrieta took him deep anyway.

Bumgarner said a select few rival pitchers justify “tougher” pitching because they are capable of putting up a good enough at-bat that it might start a rally.

“That’s the last thing any pitcher wants to do is give up a hit to another pitcher,” Bumgarner said. “Some guys you can afford to kind of go after a little more, and some guys you got to pitch them like a hitter.”

Arrieta is on that short list.