HOUSTON — Shhh, keep it quiet, but the Washington Nationals have a secret incentive during this October run, a motivation burning deeply inside them.

Sure, everyone knows they’d love to be the first team in Washington Nationals’ history to win the World Series, and the first baseball club from the nation’s capital since Calvin Coolidge was president in 1924.

When the Nats closed out the Houston Astros, 5-4, in Game 1 on Tuesday, winning their first World Series game in franchise history, closer Sean Doolittle and catcher Kurt Suzuki solemnly shook hands on the field to commemorate the moment.

“We congratulated each other on the mound in a very serious way,’’ Doolittle said. “This is cool. This is historic. The first World Series game. The win. The save. In Nats’ franchise history. To be part of that, it feels really cool.

“This is history, man.’’

Yet, if you want to know the reason they want to win, it’s to actually ease their guilt.

You see, they’ve been on this insane October run, winning 19 of their last 21 games since Sept. 23, resulting in three wild, commemorative celebrations.

But the one perhaps most responsible has had to sit back, and watch everyone else guzzle champagne and beer, while he drinks his own personal bottle of sparkling grape juice.

Juan Soto is just 20 years old.

He can’t legally drink until his 21st birthday on Friday.

“That’s why we need to win this,’’ Nats second baseman Brian Dozier said. “We’ve done all of this celebrating with him, and it sucks, because he’s not old enough to drink.

“We need to win this so we can do this thing right.

“This guy is 20 winning a World Series game for us.’’

Soto has yet to buy his first legal drink, but if the Nats continues this magical ride, he will be the toast of the town.

WORLD SERIES: 20-year-old Juan Soto lifts Nationals in Game 1 win

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CRITIC: Springer defends himself for not running out the box in Game 1

“It’s scary how good he is,’’ Nats outfielder Gerardo Parra said. “You hate to compare anyone to Mike Trout, because there’s only one Mike Trout.

“But if he keeps doing this, I’m telling you, he’s going to be better than Mike Trout."

Soto put his talents on baseball’s biggest stage at Minute Maid Park, and stole the show.

No one could stop talking about him.

Let's see, he hit a 417-foot, opposite-field homer in the fourth inning, becoming the second youngest player to homer in his World Series debut, behind Andruw Jones.

He hit a two-out, two-run, opposite-field double in the fifth inning, becoming the second-youngest to produce two extra-base hits in a World Series game, behind only Jones.

And he became the youngest player in postseason history to homer and steal a base in the same game.

Just another night for the kid.

“I don’t think he realizes the history behind this,’’ Doolittle said, “because he wasn’t even born yet when the Nats moved to D.C.’’

Well, to be technical, he was 7 at the time, living in the Dominican Republic, but sorry, he wasn’t quite up-to-date on his baseball-franchise relocation history.

And, sorry, he had no idea that it had been 86 years since a Washington baseball team won a World Series game.

“Juan’s grandfather,’’ said first baseman Ryan Zimmerman, the first player in Nats’ history, “probably wasn’t around.’’

Now, the kid who was discovered in the Dominican by Johnny DiPuglia, the Nationals vice president for international operations, is on his way to becoming the face of baseball.

Certainly, he’s the new Bryce Harper in Washington, and virtually single-handedly has kept their World Series hopes alive.

The Nats were four outs from being eliminated in the wild-card game against Milwaukee until his bases-loaded, three-run single.

They were six outs away from going home in Game 5 of the NL Division Series when he homered off three-time Cy Young winner Clayton Kershaw, tying the game, and winning it in the 10th inning.

And, on this night, he was the one who made Astros co-ace Gerrit Cole look human, with Cole losing his first game since May 22, snapping a 25-start streak in which he went 19-0 with a 1.59 ERA.

“He was clearly the key guy that we couldn't control tonight,’’ Astros manager A.J. Hinch said. “His bat speed is electric. His energy and his body is as advertised. He's calm in the moment. Clearly this is not too big a stage for him.

“He was the difference in the game.’’

Really, he’s the difference in their season.

Soto hit 34 homers with 110 RBI and a .949 on-base percentage during the regular season, and his .403 on-base percentage the last two years is the fifth-best in baseball.

And he’s just getting started.

“It’s a blessing from God to be here in the big leagues,’’ Soto said Monday, “and play baseball like I have. I never thought I’d be this talented of a player.’’

The Nationals are reveling in his success.

“Geez, man, it’s like he wants to get in a couple more homers and extra-base hits before he turns 21,’’ Doolittle said, “so he can have all of the records for a 20-year-old in the playoffs."

The Astros, who share the same spring-training complex in West Palm, Florida, are believers.

“I feel like in the last 24 hours,’’ Astros catcher Martin Maldonado said, “I’ve seen Soto more than my wife. You have to prepared, you have to do scouting reports on it. That guy’s good. He’s very good. The numbers he put up this year and last year are amazing.

“For a young guy like that. …’’

He’s a 20-year-old with the maturity of a 30-year-old and the plate discipline of a 40-year-old.

“I don't even look at him as young until you see his face,’’ Hinch said. “He's got kind of the 'it' factor. He's got the twitch. He's got fast hands. He's got no fear.

"It looks like he's completely in control of enjoying the moment.

“He's mature. Don't let the age fool you.’’

Pressure? Nervousness?

You kidding?

Not Soto.

“Sometimes I just put gum in my mouth,’’ Soto said, explaining his mode of relaxation, “but most of the time just take a deep breath and focus. It's just the pitcher and me. Everybody around, I forget about everybody around.

“I just think it’s a fight. Just the pitcher and me. That's how everything comes down.

“I just try to enjoy it.’’

And, oh, will they ever, tossing away that grape juice, dousing Soto with all of the champagne and beer they can find, and even watching him partake.

Says Dozier: “To have our first drink with him during a World Series celebration, man, how sweet will that be?’’

Follow Bob Nightengale on Twitter: @Bnightengale