BOSTON — It was brisk and windy during batting practice Monday, and the skies were black over old Fenway Park. Reggie Jackson smiled. “October weather,” he said, as nobody else on the planet quite could.

It was 44 years to the night since No. 44’s masterpiece: A three-homer outing for the Yankees in the clinching game of the 1977 World Series. That was when Jackson became Mr. October, the nickname stitched in orange on the side of the navy cap he wore before Game 3 of the American League Championship Series.

The navy color fits, but the orange is new. Jackson, 75, joined the Houston Astros in May as a special adviser to the team’s owner, Jim Crane, whose Astros trailed the Boston Red Sox in the series, two games to one, ahead of Tuesday night’s Game 4 at Fenway.

Crane and Jackson have been friends for more than 10 years, bonding over golf and classic cars in Pebble Beach, Calif., where Crane had a home. Jackson, who also lives in Southern California, has worked there for Crane, too.

“One day he said, ‘Do you want to play golf tomorrow?’ and I said, ‘No, I’ve got a match, the club championship,’” Crane said. “He said he’d come caddy for me, and I said, ‘Reggie, you don’t have to do that.’ He said, ‘No, I want to see how you are under pressure.’”

Pressure was fuel for Jackson, who hit .357 with 10 homers in five World Series wins for the Oakland Athletics and the Yankees. On Tuesday, he said the Astros seemed relaxed in their clubhouse, and that his role was to reassure them.

“Everybody gets doubt once in a while,” Jackson said. “No matter how good you are, no matter how well you’re playing, it’s always nice to hear something positive from someone that’s been down the road you’d like to go. I played with great players and had a lot of support, so when a player struggles a little bit, it’s a big help when he can look through experienced eyes and a guy says to him, ‘Don’t worry about it, you’re going to be all right.’”

Even before he joined the Astros, Jackson avidly watched their games. In the press elevator after Game 5 of the 2017 World Series — a tour de force by second baseman Jose Altuve — Crane proudly showed a text message from Jackson.

“Altuve, the best player in the game,” read the message. “Says who? Says Mr. October.”

Jackson was a Yankees adviser then, a role he had held since 1993, the year of his induction to the Hall of Fame, where an interlocking NY logo is etched on his plaque. Jackson was more influential at some points than others with the Yankees, but he was a regular presence in spring training, the postseason and at various points in between. He stepped back from the team after last season but remains on good terms.

Jackson played for four franchises in the era before interleague play — the Athletics, the Orioles, the Yankees and the Angels — and never even faced the Astros, who were in the National League at the time. Asked if it felt strange to be with them in October, and not with the Yankees, he paused.

“It feels good,” he said. “It feels good. It’s the right person, the right guy for me to be with.”

Jackson, whose charity foundation has funded science, technology, engineering and math curriculums for underprivileged children, has worked with Crane on community initiatives in Houston, including those promoting diversity and inclusion. Crane is not the blustery agitator George Steinbrenner was — no modern team owner is — but Jackson said there were traces of the old Boss.

“He’s very involved, very similar to George by being involved and making decisions to run the club, trying to make it better all the time,” Jackson said. “He’s got empathy and he’s got care.”

Crane bought the Astros in 2011, when the team had the worst record in the majors, and hired Jeff Luhnow from the Cardinals to run baseball operations. Luhnow embarked on a full-scale overhaul, with a data-driven approach to scouting and player development that has helped the Astros to a long run of contention, including a World Series title in 2017.

Crane fired Luhnow and Manager A.J. Hinch after revelations of an illegal electronic sign-stealing scam that tainted the championship. The players were spared punishment in exchange for cooperating with the league’s investigation, but they are regularly booed on the road. Jackson can relate to that, and said the Astros’ success — this is their fifth consecutive trip to the A.L.C.S. — would make them a target anyway.

“It doesn’t bother them,” he said. “I was a villain my whole career. Wherever I went with the Yankees, I was the villain. When you’re on the winning team, you’re bothering people; they don’t like it.”

Shortstop Carlos Correa has fit neatly into the villain’s role for the Astros, in ways familiar to Jackson. Correa is productive, speaks his mind and seems to crave the spotlight. He also had the same postseason batting average (.278) and home run total (18) as Jackson through Game 3. (Jackson had a slight edge in on-base plus slugging percentage, .885 to .883.)

“I talk to him all the time,” Correa said. “I joked around with him: ‘I tied you in homers,’ and he was laughing. I was like, ‘Give me some more, you’ve got plenty.’ We always have a good time. I love Reggie, he’s a great guy to have around. I learn so much from him.”

Crane wants to learn more, too. He counts two other Hall of Famers, the former Astros Jeff Bagwell and Craig Biggio, among his advisers, and said he was planning to expand their roles.

“We’re going to use them a little more on the drafting side before we draft guys, to get a better look from a player’s perspective, because a lot of the guys we’ve got that are making those decisions never played,” Crane said. “I played a little bit in college and you have to know that experience, and they know it to a very high level. They can see what’s inside of guys sometimes or where he’s coming from, where it’s not all analytical.”

Jackson was the second overall pick in the 1966 draft by the A’s — after the Mets took Steve Chilcott, a catcher who never reached the majors — and clearly lived up to the hype. So has Correa, the first overall pick in Crane’s first draft, in 2012. Correa will be a free agent after the season and stands to make a fortune on the open market.

Jackson knows a bit about that, too, and Correa is well aware.

“I will have that conversation with him when the time arrives,” Correa said. “I’m just focused on winning right now.”