ATLANTA -- If you stick around the Phillies clubhouse long enough, you’ll hear a bevy of nicknames that span the spectrum between standard and ridiculous, where it sometimes feels like you may need an encyclopedia to navigate them all. However one nickname, the concise and precise “Diaper,” is an instant dead giveaway.

That moniker is reserved for Orion Kerkering, the Phillies’ No. 7 prospect per MLB Pipeline whose debut brought tears to his father’s eyes and left Philadelphia fans daydreaming about his potential. After two brilliant postseason cameos -- the latest being a glittering inning-plus of work in the seventh and eighth innings of the Phillies’ Game 1 victory over the Braves in the National League Division Series -- it’s looking as though the sky's the limit for the man they call “Diaper.”

In just two weeks, the 22-year-old has appeared as a revelation for Philadelphia’s bullpen, a timeline that would be a dizzying whirlwind for any other rookie. But not Kerkering.

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“[I’m] for sure past it,” Kerkering said after Saturday's 3-0 win. “When the first outing is out of the way, and you’re just able to experience everything. So [I’m] just able to have fun with it now.”

To say Kerkering has had only a “cup of coffee” in the Majors would be an understatement to say the least. After he was called up on Sept. 22, he made just three appearances before vaulting onto the Phillies' postseason roster. And while other managers may be scared off by the potential fools’ gold within small sample sizes, manager Rob Thomson decided he had seen enough to not only include him in the postseason plans, but to call his name in high-leverage spots.

Who could blame Thomson? Kerkering is blessed with an extraterrestrial sweeper that averages 18.6 inches of horizontal break, according to Statcast, complemented by a blistering sinker that has an average velocity of 97.8 mph, twisting batters into knots just five appearances into his career.

But what has impressed those around the Phillies the most is not the makeup of Kerkering’s stuff, but his mental fortitude when he’s on the mound. There’s a steely coolness that’s been apparent from his first appearance in the Majors.

And according to a reputable source, he’s always been this way.

“That’s just how he is, man,” Todd Kerkering, Orion’s father, said after Game 1. “I’ve seen him emotional a few times. … Like where he’s been [angry]. I’ve seen him step back off the mound, calmly collect his thoughts, almost to say, ‘OK, let’s get back to work.'"

That same stoicism has persisted in his first two postseason outings. In Game 2 of the NL Wild Card Series against the Marlins, Kerkering became the youngest Phillie to appear in the postseason since Marty Bystrom in 1980, working a scoreless inning and notching a strikeout against Jesús Sánchez.

Kerkering then worked another scoreless seventh inning against the Braves, then exited after walking the leadoff batter in the eighth. To the onlookers, whether it be the fans or his teammates, Kerkering seemed unmoved by any magnitude of the moment.

“Between both celebrations I’ve been like, ‘Are you kidding me? I had to wait eight years to make the playoffs. You step in and, in three days, you’re pitching big innings and being successful in the postseason?’” J.T. Realmuto said. “But it’s incredible what he’s doing. Honestly, he’s so calm out there. You’d never know that he's, what, 21, 22 years old?”

In just two weeks, Kerkering has cemented his place amongst a battalion of flamethrowing veterans, and he undoubtedly will be a key cog if the Phillies are able to put together a substantial run toward the World Series.

“I think the most impressive part is his heartbeat,” said veteran reliever Jeff Hoffman, the man who referred to Kerkering as “Diaper” during his postgame interview. “He doesn’t seem to waver. … Every day, he’s the same guy -- that’s really impressive that his heart rate doesn’t spike or anything, especially this late in the season.”

To the rest of the Phillies' staff, Kerkering’s ability to remain calm is a rarity, as if they’ve found a diamond in the rough. But the youngster downplays the big moments, the interruptions and sold-out crowds at every turn.

Kerkering’s father recounted a big showcase tournament in high school when his own stomach was in knots, all while Orion showed zero signs of stress -- even with top prospects and scouts surrounding him.

“[I] just kind of go with it no matter what,” Kerkering said. “Because there’s always people that are going to ask these questions to [understand] where I’m at. I kind of have fun with it and go with it.

“I keep every moment the same no matter what, whether we’re up seven, down seven or a tie ballgame. Just keep it the same mojo.”