The Astros’ Secret Weapon? A Catcher Who Hit .172.

HOUSTON — One of the most important people on the Houston Astros was one of the worst at his position in baseball.

Among players with at least 400 plate appearances during the regular season, Martín Maldonado ranked dead last among catchers with a .172 batting average — and second last among all batters. His team led the majors in scoring despite playing one batter short on offense: He was 1 for 15 (.067) in a division series against the Chicago White Sox and then was 1 for 14 (.071) during the American League Championship Series. Regardless, the Astros beat the Boston Red Sox to advance to their third World Series in five years.

Toss all that aside and Astros closer Ryan Pressly can explain why Maldonado — for reasons entirely unrelated to hitting — is so integral to a team whose pitching staff delivered admirably despite lacking the star power of the past.

“We could be on a four-hour flight back from Anaheim or from the West Coast, and you’ll see the whole plane just completely dark, but there’ll be one light on and it’s him down there doing scouting reports,” said Pressly before the Astros kicked off the World Series against the Atlanta Braves on Tuesday at Minute Maid Park.

“That guy has put in more work probably than anybody on this team,” he continued. “He’s our quarterback back there. We can have a scouting report on one guy, and they’ve made an adjustment, so now we need to make an adjustment, and that guy back there knows how to do that. He’s truly a blessing.”

So much is asked of catchers. You must understand the hitting tendencies of all of your opponents’ batters. You have to shepherd your teammates on the mound and calm them during tense moments. You crouch behind the plate for several games a week and you’re expected to throw out any would-be base stealers. Oh, and you have to hit, too.

In many of those ways, Maldonado, 35, epitomizes the modern catcher. His teammates and coaches commend his communication skills. A Puerto Rican native, he is bilingual (English and Spanish) so he can help any of the Astros’ pitchers. He sits alongside the team’s video scouts before games and, just like them, dissects footage and numbers to understand how to neutralize opponents.

“He’s basically what you hope for in a catcher for an organization,” said his catching teammate Jason Castro.

“One thing we haven’t figured out in the game of baseball is how to put a value on leadership and in preparation,” added reliever Kendall Graveman. “And if there was a way to do that, Martín Maldonado would be the highest rank in my mind in the league. I haven’t been around everyone, but I’ve been around enough to say that his preparation before games is top notch.”

A 27th round draft pick and late bloomer, Maldonado made his major league debut with the Milwaukee Brewers when he was 25. Long known for his defense (his nickname is Machete because he cuts down base runners) rather than his offense (he has a career .212 average), he has bounced between five major-league teams. But since 2018, he has spent most of his time with the Astros, crouching behind the plate for four straight playoffs runs.

“Your catcher is your field general,” Astros Manager Dusty Baker said. “He is invaluable.”

In those past campaigns, though, the Astros had star pitchers in their prime like Dallas Keuchel, Charlie Morton, Gerrit Cole, Justin Verlander or Zack Greinke.

This year, the Astros have reached the World Series in large part because of an offense led by star hitters like Carlos Correa, Jose Altuve, Alex Bregman and Yordan Alvarez. Their pitching staff, though, is without aces Lance McCullers Jr. (he strained a forearm muscle two weeks ago) and Verlander (out all season with Tommy John surgery). Some of their most important pitchers during the regular season and postseason are much younger and inexperienced: starter Framber Valdez, 27, and starter Luis Garcia and reliever Cristian Javier, both 24.

“People laughed at me when I said he’s our M.V.P.,” said Astros pitching coach Brent Strom, whose only holdover from when he took over in 2014 is McCullers. “There was some stuff on Twitter, ‘The guy must be a drunk’ or ‘The guy must be stupid.’ But to me, he’s my M.V.P.”

The Astros value Maldonado so much that in April they re-signed him to a $5 million contract extension through 2022 with a club option for 2023, when he would turn 37.

“I take pride a lot in my defense on a daily basis and the communication I have with my pitchers,” Maldonado said. “I’m out there for them.”

Valdez, who will start Game 1 for the Astros, said Maldonado had taught him how to pitch, and how to read batters’ swings and reactions for clues of how to get them out. He said Maldonado had sat him down before starts to go over his previous game pitch by pitch. And it helps that Maldonado doesn’t need a teammate or coach or interpreter to serve as a language intermediary on or off the mound.

“During games, he just comes up by himself,” Valdez said. “That way others don’t have to translate and I don’t get messed up. And even with the gestures he makes behind the plate, I know what I have to do.”

Before last year’s A.L.C.S. against the Tampa Bay Rays, during which the Astros fell one win short of another World Series trip, Maldonado sat with relievers Enoli Paredes and Javier at the team hotel and walked them through the tendencies of each rival hitter.

Castro, who is in his 11th major-league season, said he and Maldonado had come up in an era of baseball where catchers sifted through their own statistics and video to prepare for games, compared to now, when teams have several people dedicated to producing detailed reports. He said Maldonado’s preparation was “on another level.”

When the Astros are at home, Maldonado spends his time at home with his children, Graveman said. But when at the stadium or on the road, Maldonado is glued to the screen.

“If we’re on the road, I’ve been to his room and he’s up in the morning studying,” Graveman said. “And that’s also during the season, not just in the postseason. And it’s something that no one notices if you’re not inside.”

When on the mound, Pressly said “98 percent of time” he throws whatever pitch Maldonado signals. Valdez estimated that the number was lower for himself. Graveman said Maldonado tells him that because he is the one throwing the ball, he ultimately has the final say. Whatever Maldonado can do at the plate himself is secondary.

“He wants the best out of every single guy,” Pressly said. “He knows how to talk to some guys. Some guys need a little bit more of a stern talking to. He knows what to do and what to say. And honestly, I can see him being an outstanding manager later on down the road.”