Miles Mikolas turned to the Washington Nationals’ dugout, chewed his gum and grabbed his crotch. The St. Louis Cardinals starter, having escaped a bases-loaded jam in the fifth inning of the National League Championship Series opener, seemed to be telling the hitter he had just retired that he didn’t appreciate his antics. The gesture was appreciated by the player who instigated it.

“I’m just going to laugh about it,” Juan Soto said.

The Nationals’ 20-year-old phenom had adjusted himself toward Mikolas earlier in the at-bat as part of the elaborate between-pitch routines he began as a minor leaguer. Soto used to say it was a personal thing, what has become known as the “Soto shuffle.” Most often it looks like this: He squats in his stance and sweeps his feet through the batter’s box in a sort of solo, sidewinding salsa. He stirs up dirt and — sometimes — trouble with the pitcher, a byproduct of something bigger happening in baseball. But he always has insisted he needs the routine for practical purposes because it syncs up his timing. He can’t help it. It’s a tic.

But then, a few days ago in Los Angeles, Soto revealed an ulterior motive.

“I like to get in the minds of the pitchers,” Soto said. “Because sometimes they get scared.”

It worked in the minors, so he continued it in the big leagues. On Friday, in the Nationals’ 2-0 win, Soto did more than a simple leg sweep. He took some moves from his post-take routine throughout the season — stepping forward to hack a huge practice cut, wiggling his upper body and grabbing his cup — and turned them up. He pawed at the dirt, shimmied his shoulders and grinned. He licked his lips at Mikolas after the veteran right-hander missed with a curveball. He had done something similar to Milwaukee Brewers reliever Josh Hader before delivering the decisive hit in the eighth inning of Washington’s wild-card win. It wound up turning the Nationals’ first NLCS game into a junk-holstering contest on national television.

Fellow major league players, watching from the couches like everyone else, noticed. “Mikolas did it back to Soto. Who saw it?” Andrew McCutchen tweeted.

“I was just having fun,” Mikolas said later, smiling. “He’s a great hitter; great hitters have routines. That’s part of his routine, his shtick.”

The shuffle figured to sharpen into focus in the NLCS because it fundamentally conflicts with a brand of baseball traditionalism embodied by the Cardinals. Mikolas might’ve played it off as a laugh, but St. Louis has several veteran players, such as catcher Yadier Molina, starter Adam Wainwright and reliever Carlos Martínez, who hold sacred baseball’s “unwritten rules.” Cardinals fans do, too — Soto was heavily booed when he walked back to the plate after a botched bunt attempt in the fourth inning. The most notable of those invisible commandments around the league this season is “don’t admire a home run,” and Soto’s shuffle seems to violate the “Don’t show anyone up” rule. This tests the Cardinals, who have already established themselves as this postseason’s anti-showboat task force.

Tensions escalated between Martínez and Ronald Acuña Jr., the Atlanta Braves’ young star, after Acuña was slow around the bases following a home run off the closer in Game 1 of the teams’ NLDS. Acuña had been criticized before for similar perceived violations of the unwritten rules. Pittsburgh Pirates announcer and former pitcher Steve Blass notably intimated pitchers might have thrown at Acuña “back in the day” for “all the jewelry and all the stuff.” Martínez finished Game 1 by screaming at the Braves’ dugout, and he told reporters of Acuña: “I wanted him to respect the game and respect me as a veteran player.” Martínez later added he was emotional following the recent death of someone close to him in the Dominican Republic.

The friction never subsided — Martínez threw up-and-in twice when he faced Acuña in Game 3 — and the situation hinted toward clashes around the league between styles of play. Soto understood these customs and the Cardinals’ position because in the two series between the teams this season, Molina had chirped at Soto for spending too much time out of the box between pitches. But Soto sees an advantage in landscaping, so he refused to give it up. Teammates recommended he dial it back. He decided to pick his spots.

“That’s what I’m trying right now,” Soto said. “Everybody wants to get the job done [in big moments], and if you get a little bit of that [intimidation] and get a little bit comfortable with that [shuffle] . . . you get one step in front.”

Nationals Manager Dave Martinez anticipated this approach might not go over well. When asked before Game 1 what he thought about it as an old-school player himself, he started, “I thought, you know . . . it’s a little, you know . . .” He stopped.

“But then, after talking to him and watching him, it’s a routine that he uses to get to the next pitch,” Martinez continued. “I mean, when you talk to him he really feels like that’s his batter’s box, he owns that batter’s box. And when he does that, it’s basically just saying, ‘Hey, I’m going to get back in here and I’m going to get ready to hit the next pitch.’ ”

What was a big deal Friday night sometimes isn’t because of the personalities involved as players police themselves. In the second half of last season, Soto shuffled against Aníbal Sánchez, a Braves starter who signed with the Nationals last offseason and out-dueled Mikolas in Game 1. The move surprised the veteran right-hander. He had never seen anything like it.

“I’m like, ‘What’s going on here?’ ” Sánchez said. “I thought this guy was going to fight with me. It was kind of funny to me at that point.”

Sánchez, as relaxed as they come, started laughing. He couldn’t stop and eventually Soto joined in. Soto never got a hit off Sánchez in six tries, so he stopped shuffling. He noticed later that, whenever Sánchez saw him on a non-start day, he jokingly shuffled back at the rookie.

The moment with Mikolas, in retrospect, was like that for Soto. He didn’t begrudge Mikolas’s gesture because the pitcher had gotten him out. Whatever respect the two players forged, Busch Stadium’s scrutiny on Soto still intensified. He heard louder boos than any other National when he walked to the plate later in the game, but he never let up.

In the ninth, after a wild pitch, Soto jogged toward second and tip-toed the last few steps. He put his right foot on the base, swung his head right, then left, then right again, looking at the infielders. It was as if he wanted to remind them he was here to stay.

Matt Crossman contributed reporting to this story.