This story was excerpted from Jordan Bastian’s Cubs Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

The first act of top prospect Pete Crow-Armstrong’s career with the Cubs was to don a helmet and hustle to first base as a pinch-runner in the seventh inning on Monday night. Up on the massive Coors Field scoreboard, the rookie outfielder was introduced into the displayed lineup simply as, “Unknown PR.”

“That’s hilarious,” Crow-Armstrong said with a smile. “That’s good stuff.”

Coors Field was packed with plenty of well-versed Cubs fans, who made sure people learned quickly about this “unknown” runner. When the center fielder stepped to the plate for his first MLB at-bat in the ninth, alternating chants of, “P-C-A!” and “Let’s go, Pete!” broke out in different sections.

Crow-Armstrong showed exactly who he is -- and why the Cubs summoned him to the big leagues -- with a pair of spectacular catches on Tuesday night. MLB Pipeline’s No. 12-ranked prospect has 80-grade defense and plus speed, which are traits that could help Chicago in the last two weeks, and potentially in October.

That said, the 21-year-old Crow-Armstrong is not a finished project.

“There's teachable moments,” Cubs manager David Ross said. “There's things he's got to follow and understand, a process that we have here that is important. And prospect baseball is different than winning baseball, right? He's got to learn that. He’s coming into a group that we're willing to help him out as a coaching staff, and as his teammates, because he's very valuable.”

Some teachable moments did arrive early, too.

In Monday’s win, Crow-Armstrong was thrown out trying to steal third base by one of the better defensive catchers in baseball in Colorado’s Elias Diaz. On Tuesday, Diaz nabbed the rookie at second base after he tried to move up on a ball in the dirt. Wednesday’s loss featured a sacrifice bunt gone wrong and a fly ball lost in the tough Colorado sky. The rookie went 0-for-7 in his first three games.

“Rookie mistakes are a real thing. I made them, too,” Cubs center fielder Cody Bellinger said. “The best way to learn is to kind of make those mistakes. For me, I was up in April my first year, so I had a whole season. He's up in the middle of September. It's a little different.

“But he understands that we're all here rooting for him and we're all here pulling for him. And the guidance is there to help him through situations.”

Crow-Armstrong has already been diving into conversations with third-base and outfield coach Willie Harris and first-base coach Mike Napoli. Harris, in particular, has been reaching out to the outfielder for the past few months, shooting him encouraging text messages and bits of advice.

One of Harris’ messages to a hyper-competitive kid who plays full throttle has been to know when to slow down.

“If you've already worked on slowing things down,” Harris said, “when you get here, the game doesn't speed up on you. He’s got sick ability -- sick ability. He just made me one of the best outfield coaches in baseball. I’m looking forward to watching him play, excited that he’s here and getting a chance to live out his dream.

“And I’ll be here to support him -- someone he can lean on. He can dive into me for whatever he needs and I’ll stay out of his way and let him do his thing. But when it’s time to work, we’ll work.”

Crow-Armstrong has already appreciated that approach.

“I've always loved how the organization has vocalized their plans for certain players,” he said. “And yeah, I just really appreciate the faith they've had in me and the trust they've had in me -- enough trust to go out and play center field in a playoff race. … However I can help and however I can learn is what I’m trying to get out of this.”