MIAMI — Brodie Ball, Bro Ball for short, was a disaster the first half of the season for the Mets.

No one must turn it around quicker than neophyte general manager Brodie Van Wagenen if the Mets are ever going to be a relevant franchise.

Van Wagenen needs to make trades that build for the future — using Zack Wheeler, Todd Frazier and really anybody else not named Pete Alonso, Michael Conforto or Jeff McNeil on the major league roster — after giving away the future with his big offseason splash, acquiring failed-closer Edwin Diaz and aged second baseman Robinson Cano for the high cost of young outfielder Jarred Kelenic and pitcher Justin Dunn.

It is the oldest mistake in the baseball book. New GM gives away new talent he knows nothing about.

He must be accountable for his blunders after blaming others for the Mets’ mistakes in the first half, taking it out on every one from proven pitching coach Dave Eiland to an office chair to making Mickey Callaway his managerial puppet.

Van Wagenen came into the job in spring training saying management works for the players, not the other way around, and by doing so undercut Callaway and created an atmosphere of players running to management — Brodie — if they didn’t like the way certain things were handled.

It was Van Wagenen and his trusted analytical lieutenant, assistant GM Adam Guttridge, who made the decision to bring back Jeurys Familia, against the advice of some of his baseball people who had already seen this show fail in New York.

The mistakes list goes on and on (Invisible Man Jed Lowrie) and I’m not even going to mention “Come Get Us!’’

There is nothing wrong with Brodie Bravado as long as he has a handle on the subject. So when the post-All-Star portion of the season gets underway Friday night, so fittingly against the Marlins, Van Wagenen needs to clean up his act and needs to do it quickly so the Mets aren’t burdened for a generation of bad baseball with more Bro mistakes.

When Van Wagenen says, “We all have to be better and it starts with me,’’ which he most certainly has been coached to say Friday, now that he finally grants an interview to Brodie-starved reporters at Marlins Park, this time he has to mean it.

The mirror can be a lonely place, but when your team is 40-50 there is nowhere to hide. When you fire the pitching coach to jumpstart a less-than-mediocre team and your team goes 5-11 after the change, it is on you in every way.

Putting Brodie (Out of the Box) Van Wagenen in charge was COO Jeff Wilpon’s idea, and if this continues to tumble downward Wilpon will have to make a change to get out from under this mess.

Van Wagenen has been a deal maker during his successful career as an agent, well it’s time to make some good deals. The big difference: In his past career he cut deals making life better for his individual clients.

It’s a whole new ballgame when you have to think team instead of dollar signs for your individual clients.

Get this straight, Brodie: Players work for the team. The trick is to get talented players who will come together on the field as a team. The trick is not to load up your front office with “name’’ advisers. Baseball is about substance, not splash.

Perhaps Van Wagenen learned that lesson the past few months of terrible baseball by the Mets, who can see only one team below them in the National League, the 33-55 Marlins, who are being rebuilt from the ground up by Derek Jeter in the hopes of a sunnier baseball tomorrow in South Florida.

Trading Wheeler as quickly as possible for future talent is Step 1 of the reclamation process. Instead of “Come Get Us” it should be “Come Get Him.” If Van Wagenen can use his Boston connections within his organization to make that happen or to get the Yankees or other contenders to bid more for Wheeler, that will be the start of second-half trade success that will most benefit the Mets.

Look in that mirror, Brodie, and learn from your mistakes.