COOPERSTOWN, N.Y. — On the serene veranda of the historic Otesaga Resort Hotel, Hall of Famer Dennis Eckersley was becoming animated.

Eckersley helped develop the role of the one-inning closer. He knew how tough a job it was, especially in the postseason, and that is why he was so excited to discuss Mariano Rivera’s revered place in the game.

“Listen, I can’t even put myself in the same category, I’m serious, I’m not trying to be Johnny Humble at all, this guy is in his own league, more than anybody,’’ Eckersley told The Post on Saturday.

Come Sunday, Rivera, the first unanimous selection to the Baseball Hall of Fame, will join the best-there-ever-was club.

“I’m a rookie in this thing,’’ said Rivera, who saved 652 games for the Yankees.

As for the other closers in the game, such as Eckersley, Goose Gossage and Trevor Hoffman (who was inducted last year), Rivera said: “They are way ahead of me. I can never put myself with any of them, I am just happy to be here.’’

Even though you were a unanimous selection?

“Even though I was unanimous, yes,’’ Rivera said. “I never even thought I would make any All-Star teams. … I played to win championships and that’s what I was focused on. The rest was just blessings from the Lord.’’

That is the essence of Rivera. He understands his place in the universe.

“Look at the numbers,’’ Eckersley said. “Beyond the numbers, which are incredible, are the postseason numbers. That is sick. The 0.70 postseason ERA, the 141 innings, that’s like the greatest year I ever had times two and it was in the playoffs.’’

There were 42 postseason saves. Rivera wasn’t perfect in the postseason, of course, but he was close — and he has the five rings to prove it.

“Ultimately,’’ Eckersley added, “it’s about the Ice Man for me. Because of the way he handled it. We’re two different people. I’m like ‘Aghh’ he’s like so cool, which I’ve always been envious of and I think everybody is. And to do it in that environment, having to pitch in Yankee Stadium. He handled everything with class.’’

The Yankee made sure to praise The Boss, George Steinbrenner.

“I know for sure,’’ Rivera said, “he would be proud of me. He would say, ‘Kid, great job.’ He always called me Kid.’’

How much does Rivera want to see Steinbrenner in the Hall.

“Oh, my God,’’ Rivera said, “if I had to give it all, I would do it.’’

Jackie Robinson is the one Hall of Famer he would have loved to have met.

“Mr. Jackie was the guy, but he has already passed,’’ Rivera, No. 42 said of the 42. “As a minority, he gave everything he had to come in and he did it with class. For me to be a minority and wear his number, is something special.’’

When someone joked Robinson could not have handled Mo’s cutter, Rivera said: “He would have. I would have put it in there for him.’’

Harold Baines, the late Roy Halladay, Edgar Martinez, former Yankees teammate Mike Mussina and Lee Smith also are going into the Hall, but this is Rivera’s party.

For this weekend, Cooperstown has become Mo-town.

“I might have to have a whole army around me to walk around here,’’ Rivera said with a smile.

As for how the game has changed, Gossage noted: “It took a one-inning pitcher to get a unanimous vote. I’m just saying that’s how different the game is today, you telling me that Babe Ruth and Lou Gehrig and right on down the list of great pitchers shouldn’t haven’t gotten 100 percent of the vote. There are 100 guys that if they pitched just the ninth inning they would have been unanimous. It’s not a knock on Mariano. My God, Mariano’s accomplishments are fabulous and I’m so happy for him.’’

When things did go wrong in the postseason, Rivera said: “That’s part of the game. I understood those moments are going to happen in the World Series, happen in the playoffs, and it happened during the regular season. I understood all that, so I would just have to forget it and move on. Good or bad you have to forget it.’’

Derek Jeter will be here Sunday as well and in 2020. Rivera said he is looking forward to welcoming Jeter into the Hall.

As the game continues to evolve, Rivera, the Greatest Closer, is now the opener for Jeter.