It’s a rainy Sunday afternoon in early June. The tarp is on the field at Bethpage Ballpark and the Ducks’ series finale with the Sugar Land Skeeters is momentarily in doubt. But up on the concourse, away from the rain, Bud Harrelson is in his glory.

The Ducks’ part-time first-base coach and full-time ambassador is doing what he does best nowadays, signing autographs for the fans who have showed up on this dreary, humid day. They may not get a baseball game, but they will get Buddy.

“I do more signing than anything,” Harrelson said of his role with the team. “I think it’s neat. What else do [the fans] want? They want your autograph. They don’t even know why sometimes.”

If kids don’t know why they want Harrelson’s autograph, their parents can tell them that the guy wearing No. 3 played 13 seasons for the Mets and was their shortstop in the Amazin’ 1969 World Series.

Soft-spoken and modest, baseball is in Harrelson’s blood. The 72-year old co-owner and senior vice president of baseball operations has been an integral part of the Ducks since their inception in 2000. He managed the Ducks to an 82-58 record during their first season. Then, citing a desire to travel less, moved into his current role as first-base coach. He still throws batting practice, hits ground balls and is a sounding board for current Ducks manager Kevin Baez, also a former Met, but from the early 1990s.

Bud Harrelson in 1969 Photo Credit: ASSOCIATED PRESS / Anonymous

“He’s everything,” Baez said. “He’s the face of the organization. Him and Quackerjack,” the Ducks’ mascot. “I don’t know if it goes Buddy and Quackerjack or Quackerjack and Buddy. But it’s in that area . . . He’s one of the best people I’ve met in baseball.”

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Harrelson lives in Hauppauge, a five minute-drive to the Central Islip ballpark. He spends his days answering mail requesting autographs, playing in charity golf tournaments and following the Mets.

“I like Terry Collins,” said Harrelson, who managed the Mets (and Baez) in the early ’90s. “He’s not negative. He gets the guys going . . . It’s tough media here. When I was managing, it was so negative. They were saying everything bad and nothing good. This is a tough game. It’s up and down.”

But the Ducks are his crown jewel. Through all his Mets glory, he said that bringing the minor-league game to Long Island is the best thing he’s ever done in baseball.

“It had never happened here,” he said, as passionate as ever about the team he helped mold.

When the Ducks are on the road, he listens to them on radio or on the team’s YouTube stream. When they are home, he is either on the field or seldom more than a few rows away from it.

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“I love the game of baseball,” he said. “I don’t ever want to get out of it.”

Eventually, he will. He said he doesn’t know when, but he can see a day when trips to the ballpark are no longer part of his daily routine. But that doesn’t mean he wants to think about it.

“I don’t know much about anything else but this,” Harrelson said. “And there’s nothing wrong with that. Baseball is a wonderful game.”

The rain finally stopped and the Ducks got the game in, winning June 5, 9-1, as starter John Brownell tied the franchise mark for starts (91) and wins (40). Harrelson had planned on leaving early to attend his own birthday party — he was born June 6, 1944 — but as reporters flowed into the clubhouse for postgame reaction from Baez and Brownell, Buddy was still there. Rain or shine, he just can’t shake the game.

Plus, why go home? There might have been cake, but there was no baseball. And for Harrelson, that’s still all that matters.

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On deck

The Ducks finish a six-game road trip in Southern Maryland on Sunday afternoon. They return to Bethpage Ballpark on Tuesday for three with the New Britain Bees and four with the Lancaster Barnstormers.