Raise the white flag.

As if a matchup of two last-place teams on a crummy night in Queens wasn’t enough, the Mets had perhaps their sloppiest, ugliest loss of the season against the miserable Royals, 16-12, in a wild game to open a homestand at Citi Field on Tuesday night.

After opening a five-run lead in the fourth, the Mets gave up a dozen straight runs before getting back on the scoreboard.

It came on a night that saw the Royals hand the Mets a three-run Little League homer in the bottom of the first, thanks to three throwing errors on one play.

It came on a night that saw the Royals hand the Mets a three-run Little League homer in the bottom of the first, thanks to three throwing errors on one play.

That proved to be just an appetizer for a bizarre night, and it still couldn’t propel the Mets to a victory, as their ragtag pitching staff was no match for the Royals.

The Mets, short in the bullpen after taxing their pitching staff in back-to-back wins in Atlanta the previous two games, were forced to pitch Kodai Senga on three days’ rest for the first time in his career and then saw Austin Warren fail to retire a batter in the fifth.

That led to Long Island’s Matt Seelinger making his MLB debut in a tie game after a decade in the minors.

Interim manager Andy Green acknowledged the rough condition of the staff and said the team was “forced to make some of those triage decisions along the way.”

A truer statement probably couldn’t be made about this Mets season — until Green followed by saying the game “turned into kind of a perfect storm.”

The aftermath included the Mets falling to 200-2 in franchise history when scoring 12 or more runs, as they wasted a breakout offensive night from A.J. Ewing and a three-run homer by Juan Soto, his 20th of the season.

It began to fall apart when Senga allowed two runs in the second and a pair more in the fourth.

After Soto gave them a five-run lead in the bottom of the inning, Austin Warren entered to start the fifth and allowed all six batters he faced to reach base — and five of them to score, as Kansas City tied the game 9-9.

Warren called his outing “terrible” and noted his poor location.

Instead of the right-hander eating innings, he forced Huascar Brazobán into the game earlier than planned, which left Seelinger to make his MLB debut in a tie game, and the right-hander allowed seven runs.

The Westbury native immediately ran into trouble, as he walked Lane Thomas on four pitches and then gave up an RBI double to Salvador Perez.

Nick Loftin tagged Seelinger for a two-run shot later in the inning.

He survived and pitched a scoreless eighth, but it didn’t matter.

Coming off back-to-back close wins in Atlanta, the Mets returned to Queens, where they’d lost six of seven in their last homestand.

Looking to win a third straight game for the first time since their four-game winning streak at the end of May, the Mets instead suffered another brutal defeat.

“The season presents these challenges,’’ Green said before the game of the team’s depleted bullpen.

He couldn’t have foreseen this one coming, though.

And it doesn’t figure to get much better anytime soon for a Mets team that is already staggering to the All-Star break with seemingly no answers on the horizon.