Justin Tuck is a voice of reason at a time when the Giants fans who cheered him to two Super Bowl championships are emotional wrecks following the talk-of-the-sports-and-entertainment-world trade of Odell Beckham Jr. to the Browns. Once a Giants captain, always a Giants captain.

“Give it time,” is Tuck’s message to Giants fans. “I’ll get mad at his decision if in two years we’re still where we are. Why jump on it right now?”

In the meantime, he will trust general manager Dave Gettleman.

“I think Gettleman is doing what he thinks is best for the franchise for the long term, and I don’t think anybody can question that,” Tuck told The Post. “Everyone gets so emotional about these things, but I think all the players understand this is a business, and we need to approach it as a business, and things like this happen, unfortunately.

“Long story short, I think Odell needed a new change of scenery as well as this team needed to move on and try to get what they got for him.

“And also I think Gettleman’s looking at it from a perspective of this team had a lot of holes that he needs to find a way to fill, and they’re in a rebuilding phase anyway.

“I think it was good for both teams. I like what we got back from it, and I think it was a good place for Odell to go. He has a lot of rapport with [Jarvis] Landry out there, the young talent that that Cleveland Browns team has is attractive.

“We get the opportunity to go back to the drawing board, which I think the brass — that is what the Giants wanted to do that anyway.”

In the meantime, he will trust John Mara.

“I guarantee if you ask Mr. Mara if he wanted Odell Beckham as a Giant For Life, you’d think yes,” Tuck said. “I can pretty much guarantee that. But at the end of the day, what’s the decision made off of? What’s best for the team for the long haul. You think he’s not thinking about the long haul? This is his livelihood. This is what his family’s legacy’s built on. I know for a fact he thought long and hard before he pulled the trigger on it.”

Tuck, who will be introducing comedic talent as a celebrity presenter at the Garden of Laughs fundraiser April 2 at the Garden, said he thinks Eli Manning doesn’t have to be a Mann overboard on the sinking Big Blue ship.

“Unfortunately for us, we’re in that predicament where you have this face of the franchise that’s on his last legs when it comes to his career,” Tuck said. “Depending on what we do O-line-wise, he has probably, call it two years.

“I expect them to draft a quarterback this year. If that’s the case, why not have a guy like Eli Manning there to teach him the ropes? If I’m Gettleman, if I’m Mr. Mara and the Giants brass, I want that quarterback to learn under Eli Manning. If I’m the GM, I’m definitely going quarterback if there’s a guy there they like.”

One would think the last thing he wants to see is Manning trotted out as a 38-year-old sacrificial lamb.

“I don’t know about that,” Tuck said. “If you looked at the games last year when Eli’s protected, he was a pretty decent quarterback.”

Except now he won’t have Beckham to target.

“OK, I get that,” Tuck said. “Odell Beckham is one of the premier talents in this league. I think he’s headed to the Hall of Fame. I would venture to say that they felt as though in order to get back to being a Super Bowl-caliber team, they had to make a change. I’ll give up a superstar player any day to get four or five very, very solid pieces.”

Tuck added: “Did we have a superstar wide receiver in ’07 and ’11? I don’t remember one. I remember we had a very good group of guys who played together, and a team that played together, that’s what I remember. And I think that’s what the Giants are trying to get back to. Which I am totally fine with.”

But trading Beckham less than a year after signing him to a $90 million contract?

“I know people who got divorced in six months that were so in love, then they hate each other,” Tuck said.

His beloved Giants defense is a barren wasteland.

“I’m just a fan with an opinion,” Tuck said. “I see we need a pass rusher.”

And Pat Shurmur needs a team leader to step forward.

“You can have all the players in the world, if you don’t have leadership, you’re shortchanging yourself,” Tuck said. “That’s what I feel lacking right now. And that’s not a shot to anybody on the team right now. That is a command for people to step up. We need a bona fide leader in that locker room. There is an open job to be the leader.”

Landon Collins could have filled the Tuck-Antrel Rolle role, but Gettleman let him walk to an $84 million contract with the Redskins.

“If I’m taking emotion from it, which I’m trying to do, because I love Landon, I love how he played, I wish I could have got to play with him, he reminds me a lot of a young Antrel,” Tuck said.

“But again, I can see both sides of it, without allowing my fandom for a guy like Landon Collins to get in the way of, right? That’s probably why I wouldn’t make a good GM. He did everything that you think you’d want from a player in the Giants uniform.”

Tuck, who is VP of private wealth management for Goldman Sachs, confesses that losing Beckham and Collins was a bitter pill for him to swallow.

“The pill has been swallowed. You can’t bring Landon or Odell back at this point, you might as well swallow the pill. I’m waiting to see if that pill helps me or not,” he said.

He urges Giants fans to move on.

“I would say the years have been very kind to the New York Giant fans overall,” Tuck said. “Obviously we’ve had some down years right now, but I think you’re seeing a group of guys led by Mr. Mara who’s trying to figure it out.

“What’s your option? You can either not be a fan, or you can give it time.”