PITTSBURGH >> These Chicago Cubs are supposed to be too young to be here. Or maybe they’re just too good to care.

Jake Arrieta allowed four hits in nine dominant innings and the Cubs rolled to a 4-0 win over the Pittsburgh Pirates in the NL wild-card game on Wednesday night.

Arrieta struck out 11 without a walk. He also dusted himself off getting plunked by Pittsburgh reliever Tony Watson to send the Cubs to the NL Division Series in St. Louis starting on Friday.

“I’m exhausted. I haven’t felt this way all year,” said Arrieta, who led the majors with 22 wins. “This atmosphere, the energy was unbelievable. Tried to use it to the best of my ability. They were loud, they were really loud.”

Dexter Fowler homered and scored three times for the Cubs. Kyle Schwarber added a towering two-run shot off Pittsburgh starter Gerrit Cole as Chicago raced to an early lead and let Arrieta do the rest.

The largest crowd ever at PNC Park failed to rattle Arrieta or one of baseball’s youngest teams. First-year manager Joe Maddon’s club played with swagger and confidence and looked right at home while snapping a nine-game playoff losing streak that dated to the 2003 NL Championship Series.

“It’s tremendous for the city. It’s been a while,” Arrieta said. “Chicago’s been waiting for this, but it’s only step one.”

Pittsburgh was knocked out after finishing second in the majors with 98 victories this year. Last season, the Pirates also were shut out on four hits at home in the wild-card game, losing to San Francisco.

“Well, sports is hard. Life’s not fair. You go out and play. You get beat, you move on,” manager Clint Hurdle said.

The bearded, 29-year-old Arrieta, still unbeaten since July 25, stretched his remarkable second half — in which he posted an 0.75 ERA — into the opening round of the playoffs. He threw the first complete-game shutout for the Cubs in the postseason since Claude Passeau tossed a one-hitter in the 1945 World Series against Detroit.

Arrieta even laughed off a weird sequence in the seventh when Watson’s fastball hit him in his left side. The benches and bullpens cleared when Watson was issued a warning, leading to little more than a few heated exchanges along the first base line.

“I hit two guys, unintentionally. I’m not trying to hurt or hit anybody,” Arrieta said. “Balls were slick tonight. I just lost it a couple of times, it kind of ran away from me.”

“I expected that. They’re going to take care of their own guys. It’s understandable. Everything after that was fine,” he said.

Pirates utility player Sean Rodriguez, who’d already been pulled, was ejected and proceeded to give an unsuspecting water cooler a series of one-two combinations, eventually sending it tumbling to the ground.

Pittsburgh had no such luck against Arrieta, with Hurdle seemingly flummoxed on how to get to attack a right-hander who has matured from raw project into overpowering force.

Hurdle shelved slugger Pedro Alvarez — whose 27 homers led the team but whose 23 errors made him a defensive liability — in favor of more sure-handed Rodriguez. Hurdle pointed to the athleticism Rodriguez brought as a major factor, figuring the Pirates would need to get creative to score against Arrieta rather than hope Alvarez runs into the kind of mistake Arrieta has avoided nearly all season.

Maddon took a decidedly different approach, starting Kris Bryant in left and Schwarber in right and Tommy La Stella at third — positions each had played only sparingly during the regular season — because it was the lineup that presented the most firepower.

Did it ever.

Chicago took a 1-0 lead two batters into the game when Fowler led off with a single, stole second and scored on a single to left by Schwarber.

The two hooked up again in the third. Fowler singled with one out and Schwarber turned an 88 mph slider from Cole into a massive two-run shot that appeared destined for the downtown Pittsburgh skyline before disappearing over the stands in right field.

It drained whatever juice remained from a crowd that spent the buildup to the showdown between the teams with the second and third best record in the majors trying to get a rise out of Arrieta. The 29-year-old embraced it, tweeting back “whatever helps keep your hope alive, just know, it doesn’t matter.”

Pretty much.

Maddon has preached a “keep it simple” approach since taking over last winter. When Arrieta is on the hill, Maddon’s job tends to get pretty easy.

Fueled by sometimes impeccable control, Arrieta worked both sides of the plate — and sometimes a little more — to continue one of the most torrid stretches by a pitcher in baseball history. He threw 20 of his first 25 pitches for strikes and Pittsburgh struggled to generate anything resembling momentum.

Arrieta retired 10 straight at one point, his only real wobbles coming in the sixth and seventh. Pittsburgh loaded the bases with one out behind a single, a hit batter and an error.

Starling Marte’s sharp grounder, however, rolled right to Addison Russell at shortstop. A toss to second and a throw to first later to complete the double play, and Arrieta and the rest of his teammates were pumping their fist on the way back to the dugout.

The team with the best road record in the majors this season hardly fazed by the stakes or the weight of 106 years of postseason futility.

Another double play in the seventh and the visiting clubhouse began preparations for a raucous celebration by a group featuring a bunch of players who only recently became old enough to legally enjoy the champagne and beer that awaited them.

The Pirates, meanwhile, head into the offseason after a brief nine-inning stay. Last fall it was Madison Bumgarner and the Giants who silenced the masses in an 8-0 whitewash, on their way to winning the World Series.

This time it was Arrieta’s turn, perhaps a more alarming development considering the Pirates will spend a large portion of the next decade trying to keep up with Schwarber, Bryant and Russell as well as the Cardinals in the hyper-competitive NL Central. St. Louis led the majors with 100 wins.