As a rule, the Texas Rangers are not chill.

Most famously there’s the now years-long tradition of playful teasing between Adrián Beltré and Elvis Andrus. Other times, that hyperactivity turns into Sam Dyson precipitating a near-fight in a playoff game or Rougned Odor laying out José Bautista. Before a game, the Texas clubhouse buzzes with laughter and a seemingly unending series of ping-pong matches while the relief pitchers hold forth on Game of Thrones. Afterward, key players in Rangers victories — and, sometimes, Fox Sports reporter Emily Jones — get doused with Powerade.

All of this energy makes Nomar Mazara stand out. In a room full of big personalities, the 21-year-old outfielder speaks softly and carries a big stick — literally.

From the moment he leaves the on-deck circle, it takes Mazara about 20 seconds to get into his stance. He strolls to the plate with an even, steady gait, like a cross between a drill instructor and a debutante. He tightens the velcro straps on his gloves, bends down to touch his toes not once but twice. Then, he measures his position in the box by tapping the corners of home plate, digs in, shrugs his shoulders, and drops into his crouch.

The whole process, which is so intricate and deliberate it looks like he designed it in consultation with NASA, ends with Mazara in a wide-set, open stance, hands behind his head, bat rocking between two and three o’clock as he times the pitcher’s delivery.

When the pitch comes in, Mazara pulls his front foot toward the plate, sets, and tracks it almost all the way into the catcher’s mitt. And if he decides to swing, well …

His front foot comes down and in an instant, that 6-foot-4 machine clicks into action — his hips snap around, pulling his chest, arms, bat, and head around the axis of rotation. Before you can say “angular momentum,” the ball’s in the second deck.

It’s the only thing he does suddenly.

Mazara usually hits in front of Beltré in the Rangers’ order, and the contrast between the two at the plate can almost make you seasick. Mazara is settled and calm at the plate, his game characterized by extreme patience and long, graceful actions. Beltré, however, looks positively twitchy by comparison, hacking at anything he thinks he can reach, sometimes on one knee. It’s a Jack Russell Terrier hitting behind a jaguar.

In the Rangers’ high-energy clubhouse, Mazara’s become almost as famous for his calm demeanor as he is for his sweeping left-handed swing.

“He’s a pretty cool kid, man,” Andrus said. “His nickname is pretty on it, The Big Chill, in that he always stays quiet and he’s ready to do his work every single day.”

The pseudonymous Michael Tepid, who writes about Rangers prospects for Lone Star Ball, stuck Mazara with the moniker despite being virtually certain that Mazara had never even heard of the movie it was based on.

“It just fit his personality. He’s never too up, never too down,” Tepid said.

The soft-spoken Mazara is polite and diplomatic to the point of seeming guarded — understandably so, as a 21-year-old rookie in a veteran clubhouse, talking to reporters in his second language. His favorite thing about the big leagues? “Everything.” The teammates he looks to for guidance? “Everyone.”

“He’s great,” said Rangers center fielder Ian Desmond. “He’s got all the intangibles, he’s got unbelievable character — one of the first to the field, one of the last to leave. He’s quiet and goes about his business. He respects the older guys’ space and really just fits in. That’s probably the best part about him.”

“It’s been fun to watch his growth, to transition from the minor leagues to the big leagues and still maintain a sense of level-headedness,” said Rangers manager Jeff Banister. “He’s extremely humble, and I think he’s been able to control all the moments very well. We see his talents on the field — his talents are exceptional.”

Mazara is the youngest player on a team that’s achieved incredible success over the past few years, mostly thanks to homegrown talent. The Rangers’ current run of prosperity dates back to a class of Andrus, first baseman Mitch Moreland, and pitchers Matt Harrison, Neftali Feliz, Derek Holland, and Alexi Ogando that was just breaking into the big leagues as Texas won back-to-back pennants in 2010 and 2011. Since then, the pipeline has just sort of kept going, with Odor, left-handed pitcher Martín Pérez, and infielder Jurickson Profar coming up in the five years since. After the front office dealt other prospects to Milwaukee for Yovani Gallardo and to Philadelphia for Cole Hamels, Mazara is one of the last drops in a well that is starting to run dry.

Mazara, who came in at no. 5, was one of five Rangers to make the Baseball Prospectus top 101 this past offseason, along with centaur-like, power-hitting corner infielder Joey Gallo, lanky outfielder Lewis Brinson, bespectacled power right-hander Dillon Tate, and 2014 first-rounder Luis Ortiz, also a right-handed pitcher. Gallo’s been up and down between the big leagues and Triple-A over the past year, but none of the others are past Double-A, and Mazara is younger than all of them except Ortiz.

Less than five years removed from receiving a record $4.95 million signing bonus as a 16-year-old out of Santo Domingo, Dominican Republic, Mazara’s become — along with Corey Seager — one of the two best pure hitting prospects in baseball. That’s thanks to a combination of approach, plate discipline, power, and hit tool that landed him in the Rangers lineup two weeks before he turned 21.

Mazara debuted on April 10 as an injury replacement for Shin-Soo Choo, and sensed an opportunity to make himself indispensable to the big league club.

“I came here because Choo was hurt, so I said I’m going to do everything I can,” Mazara said. “I don’t make decisions, so I’m going to try to make it hard [for the Rangers to send me down].”

In April, he won American League Rookie of the Month, then did it again in May. In that time, Delino DeShields got sent down, shifting Ian Desmond from left field to center, with Ryan Rua taking over in left. And when Choo returned in mid-June, Mazara moved over to left field, reducing Rua to a part-time role, even as Mazara slumped. As precocious a hitter as Mazara is, though, that talent hasn’t made him exempt from the kind of adjustments that all rookies have to make.

“The league’s going to get to know him, is going to pitch him a certain way,” Andrus said. “I think he’s talented enough to make that adjustment and as long as he’s still learning and playing hard, I don’t see how anything wrong can happen.”

After tearing up the league for eight weeks, Mazara’s slumped to a .266/.330/.362 line in June, but he’s still hitting .289/.341/.437 overall.

“Everybody, once in a while, has a little slump,” Mazara said. “I’ve been hitting the ball pretty good — I just haven’t had many hits. So I’ll just try to battle, battle, and one day it’s going to come.”

In the midst of that slump, Banister is trying to keep Mazara rested and confident, even if the rookie doesn’t look bothered.

“You never know what’s going on underneath,” Banister said. “I think he does a really good job of controlling that emotion, and he’s going through a stretch here where he’s handled some challenges, and I look forward to seeing what the next stretch looks like for him.”

It’s telling that even though Mazara’s a rookie, he’s hit in important spots in the order from the moment he arrived. And Banister hasn’t dropped him in the lineup even as he’s struggled: Mazara has made 66 starts so far this year, and he’s batted second 26 times, third 28 times, fifth nine times, and seventh only three times. Mazara has the potential to be a middle-of-the-order staple for a long time, and Banister is betting that he’s there already.

“It’s not easy. Especially hitting in the spot he’s been hitting since he got here — there’s a lot of pressure on him,” Andrus said. “But like I said, he’s got a good mentality. He knows what he needs to do.”

What he needs to do is hit, a lot. Apart from his bat, Mazara offers a preposterous throwing arm and not a whole lot else in terms of defensive value. He’s already consigned to outfield corners at 21, and might ultimately end up at first base. That means that unlike, say, Andrus and Desmond, he can’t fall back on defense at an up-the-middle position if the bat starts flagging. If he’s going to be a star, he’s got to absolutely rake.

And with his size, his poise, and his hit tool, he ought to absolutely rake going forward. So if you’re worried about Mazara, you can chill out.

All stats are current through Wednesday afternoon.