HOUSTON — Seeing as he is 21 years old and not yet 30 games into his major-league career, almost every day brings a new first for Rangers rookie Evan Carter. Sunday marked a big one: first Championship Series game, and — no pressure — it was against the reigning champion Houston Astros. As if that weren’t enough to deal with, it was also Carter’s first time playing at Minute Maid Park, with its funky left-field wall jutting in and out.

Robbie Grossman, the Rangers’ backup outfielder who started his career in Houston, says it’s one of the tougher left fields in the league, “just because of all the angles.”

So when Travis Jankowski signed with the Rangers this season, Grossman gave him a tutorial on how to handle Houston’s wonky wall when they played here earlier in the year. And on Saturday, when the Rangers had a workout at Minute Maid Park, both Grossman and Jankowski took Carter out to practice fielding balls bounced off the wall and relay everything they’ve learned about navigating the angles.

“Evan is a hell of an athlete. I don't know if he needs our advice. But when he goes out and makes two great plays,” Jankowski said, “makes you kinda think, ‘Oh, maybe what we said helped.’”

The first was in the bottom of the first inning, a line drive off the bat of Alex Bregman that Carter chased down in the corner and caught just before he crashed into the Crawford Boxes. At the time, it was early in a scoreless game that seemed to favor the Astros from the outset.

Seven innings of a pitchers’ duel later, the stakes were much higher.

Jordan Montgomery and Justin Verlander had become the first two starters this October to both go at least six innings in a postseason game. Verlander — making his 36th career postseason start, second on the all-time list — was the first pitcher to record a quality start against the Rangers in the playoffs, yet he was in line for the loss after surrendering two runs. Carter scored in the second after turning what looked like a single to right into a double with his speed. Later, nine-hole hitter Leody Taveras hit a solo shot.

And that was it for offense from either lineup. On the side, Montgomery continued his campaign for Most Valuable Trade Acquisition with 6⅓ flawless frames. But a 2-0 lead for the Rangers is not the most comfortable position for them to be handing the game over to the bullpen.

After Josh Sborz (ERA in the regular season: 5.50) walked Jose Altuve to lead off the eighth, Bruce Bochy brought in Aroldis Chapman. Astros fans — perhaps familiar with Chapman’s many high-profile meltdowns at Minute Maid, where he has a 7.53 ERA in his career — seemed to delight in this development, cheering the pitching change, or at least cheering what looked to be the rumblings of a rally.

The next batter, Bregman, representing the tying run, swung at a 2-1 slider, launching a ball right at the awkward corner in left-center. A few more feet, and it would’ve been out — game tied — but even if it stayed in the park, the Astros figured to benefit from one of the best quirks in baseball: nonstandardized playing dimensions.

It was exactly the kind of play that Jankowski had warned Carter about.

“That is the one I said, ‘That's the toughest,’” Jankowski said after the game. “A couple guys hit it there in [batting practice], and just talking to him, I was like, ‘That's a tough one. That's the one you have to get around to find a wall.’”

Carter ran back, around a 90-degree turn in the wall, and leapt into a shadowed corner to catch the ball 365 feet from home plate in a spot he couldn’t have seen from where he started the play. Altuve was just reaching second base when the ball he expected to be out of the park or at least a hit landed harmlessly in Carter’s glove. Altuve scrambled to retreat to first and, in doing so, neglected to re-tag second. Marcus Semien, the Rangers’ second baseman, noticed immediately.

“We got the captain who could see everything,” Grossman said. “So once I saw he was pretty sure about it, I was like, we don't even have to replay it at this point.”

They did replay it, though, because Altuve wasn’t called out initially. But Semien was right — instead of a game-tying home run or a run-scoring hit into a tricky corner, it was a double-play. Four outs later, the Rangers won 2-0 to take the first game in the Lone Star ALCS.

“The kid Carter,” Bochy marveled afterward, “what a game he had out there.”

It’s getting difficult for coaches and teammates to find new ways to praise Carter as he continues to excel at everything on the first try.

“He told me before the game, ‘Every game I’ve played is bigger than the last,’” Grossman said, and it’s not hyperbole or a figure of speech. That’s simply the truth. Carter joined a struggling Rangers team trying to hold on to its postseason spot in early September and has done nothing but succeed as the team played stressful games down the stretch and then swept its way through the first two rounds of the playoffs.

“I feel like sometimes you gotta go out there and check his heartbeat and just see, like, ‘Are you alive? Do you realize that we're in the ALCS?’” Jankowski said. “He’s such a low-heartbeat guy, such a relaxed, calm presence. At 21 years old, not too many people have that.”

His patience at the plate and offensive output have gotten most of the attention as Carter has transformed from a surprise prospect into a key postseason contributor. But his teammates praise his defense. Both Grossman and Jankowski cited a diving catch in Cleveland his second week in the majors as the most impressive they’ve seen him make.

“That one was incredible,” Jankowski said. But: “The one in the eighth inning was probably the most important catch.”

For now, anyway. Three more wins, and Carter will be playing in his first World Series.