HOUSTON — During a lull in the sixth inning of Game 1 of the American League Championship Series on Friday, as umpires sorted out a play, Houston Astros catcher Martin Maldonado walked back to his position behind the plate. Waiting there for his turn to bat, Boston Red Sox catcher Christian Vazquez smacked Maldonado on the chest and threw his arm around him.

Although they are rivals seeking a berth in the World Series, they are close friends. But so are several others on the Astros and Red Sox. The connection: Maldonado, 35, and Vazquez, 31, are from Puerto Rico, whose population of over three million people is well represented in this matchup.

The manager of the Red Sox is Alex Cora, a native of Caguas, P.R. The stars in a 5-4 win by Houston in Game 1 were also Puerto Rican: Astros shortstop Carlos Correa, who smashed the go-ahead blast, and Red Sox center fielder Kiké Hernandez, who clubbed two home runs. After two more hits in a 9-5 win by Boston in Game 2, Hernandez was hitting an eye-popping .500 (16 for 32) this postseason. Three coaches were also born there: the Red Sox’ first-base coach, Ramon Vazquez; the Astros’ bench coach, Joe Espada; and the Astros’ hitting coach, Alex Cintron.

“It’s super cool,” Christian Vazquez said in Spanish, “and I’m so happy to play a series with a lot of Puerto Ricans.”

In all, eight players and coaches on the field and in the dugouts in this rematch of the 2018 A.L.C.S. were born in Puerto Rico. That doesn’t include Red Sox second baseman Christian Arroyo, who was born in Florida and is of Puerto Rican descent. Nor does it include the Red Sox’ assistant general manager, Eddie Romero, a San Juan native who took a moment standing in the visitor’s dugout at Minute Maid Park to take in the significance.

“It’s a huge moment of pride for back home in Puerto Rico,” he said, adding that he heard from so many family members and friends on the island after the Red Sox upset the top-seeded Tampa Bay Rays in the previous round.

“That’s one of the funniest things: You get congratulatory messages from family, but especially for Kiké and Christian and Arroyo and Alex,” he continued. “They are so proud of their own being on this stage. And I’m sure it’s the same for all the Puerto Ricans involved.”

Baseball is part of the fabric of Puerto Rico. It produced the fourth-largest group of players born outside the mainland United States (18) on 2021 opening day rosters, according to figures from Major League Baseball, trailing the Dominican Republic (98), Venezuela (64) and Cuba (19), which have larger populations.

Five players of Puerto Rican descent are in the Baseball Hall of Fame: first baseman Orlando Cepeda, second baseman Roberto Alomar, catcher Ivan Rodriguez, designated hitter Edgar Martinez and outfielder Roberto Clemente, who is considered one of the greatest players ever, regardless of origin, and was the first player from Latin America inducted into the Hall, in 1973.

Since 1989, when M.L.B. began to include Puerto Rico, a commonwealth of the United States, in its first-year player draft — rather than continuing to allow amateurs to sign as free agents, as they do in the Dominican Republic and Venezuela — many have pointed to that as a reason for the shrinking pipeline. The number, though, has recently ticked up: 20 players born in Puerto Rico were on opening day rosters in 2020, the highest total since 2011.

“We haven’t made the adjustment about the draft,” said Cora, 45, who was picked by the Los Angeles Dodgers out of the University of Miami in the third round of the 1996 draft. “That’s the bottom line. People can say that is the obstacle for us not to produce more players, but the draft has been there forever. We have to do a better job preparing our student-athletes — talking about high schoolers — to be prepared to actually get scholarships at Division I schools. And if we do that, then the draft plays to our advantage, right?”

Given the number of Puerto Ricans in M.L.B., having so many face off in this round meant a lot to the players and coaches and to their families and fans. Hernandez, 30, said everyone there has been supportive, “but no one misses the playoff games in Puerto Rico.”

“There’s going to be a lot of people in their homes watching this series, there’s going to be a lot of restaurants full,” said Espada, 46, who was born in the Santurce district of San Juan. “And in my home, too. My parents live down there.”

When Hernandez was with the Dodgers, he was often the lone Puerto Rican on the roster. His team fell in the World Series to the now tainted 2017 Astros, which featured Carlos Beltran, Correa, Cora and Cintron. And in 2018, Hernandez’s team lost the World Series again, this time to the Red Sox, who were led by Christian Vazquez and Cora.

Now in Boston with Cora and the others, Hernandez has shined as an everyday player, and he joked that he was happy to have the Puerto Rican advantage. “I feel good being on the side with the Puerto Ricans and having the support of Puerto Rico, not just for me as a player but for the team I belong to,” said Hernandez, who finally won a World Series ring last year with the Dodgers.

“The series before was a lot of Cubans,” added Correa, 27, referencing the Astros’ past playoff round against the Chicago White Sox, which featured seven players born in Cuba. “This series is a lot of Boricuas.”

While the diversity on the field isn’t always reflected in leadership positions across the major leagues — Cora was one of four Latino managers in baseball during the 2021 season, and Al Avila of the Detroit Tigers is the only Latino leading a baseball operations department — Romero said he loved that several Puerto Ricans in the series were not just players.

“We have a manager, bench coaches involved, first-base coaches,” said Romero, whose father played for the Red Sox in the 1980s. “It shows that it goes beyond the playing field and that these guys are talented enough to succeed in other areas.”

Espada said the Puerto Ricans on both sides were taking the meaning of this series “very seriously.” Although most of the Puerto Ricans on both teams know each other well — in fact, most Puerto Ricans in baseball do — Espada said they would not be talking or texting much until the series was over.

Before it began, Correa and Cora sent each other congratulatory messages. And when Cora was out of baseball last year serving a suspension for his role in the Astros’ sign-stealing scheme, Espada kept tabs on him via text.

Keeping some distance might be harder for Christian Vazquez and Maldonado, who are particularly close. They play the same position and were teammates on the Indios de Mayagüez in a Puerto Rican winter league. And Vazquez said they stay in frequent touch on a text chain with all the Puerto Rican catchers in the major leagues. Among the other active major league catchers from the island: Yadier Molina of St. Louis, Victor Caratini of San Diego and Roberto Perez of Cleveland.

“You wish them the best,” Vazquez said of his Puerto Rican counterparts on the Astros, “but at the end of the day, you want to win.”