NEW YORK - There was champagne popped at Citi Field on Sunday night.

Cases and cases, in fact.

It was, of course, used to celebrate the Kansas City Royals' first World Series title since 1985.

The Royals' 7-2 victory in 12 innings gave them the championship in five games, and they earned it by becoming the first team to win three World Series games in which they trailed in the eighth inning or later.

"You guys know what we do all season," said Royals catcher Salvador Perez, who was named World Series MVP. "We never quit. We never put our heads down.

"We never put our heads down. We never think about, 'OK, the game is over.' No. We always compete to the last out. And that's what we did tonight."

No doubt.

Yet, very easily, the bubbly could have been reserved for the New York Mets to celebrate their first World Series title since 1986.

In three of their four losses, it was bad defense that hurt the Mets, particularly in Games 1 and 4. Plus, Lucas Duda had a bad throw in the ninth inning Sunday night at allowed the Royals to tie the game. It wasn't scored an error but it could have been.

"We know they're an aggressive team," Duda said. "It was a gutsy play. I just didn't make a good throw."

So instead of a great 2-0 win for the Mets via a gem by Matt Harvey in Game 5 and staying alive for game Game 6 in Kansas City Tuesday night, the Mets were cooked.

That's why the Mets will be sick all winter, thinking of what could have been.

This isn't pie in the sky stuff or a bitter Mets fan working as a sports writer. This is legit. The Mets could have won the franchise's third championship with better play in big moments.

The Mets had Game 1 in the bag. They had a 4-3 lead with one out in the bottom of the ninth inning when Jeurys Familia gave up a home run to Alex Gordon to tie the game.

David Wright committed a big error in the 14th inning, leading to a run and an extra inning victory for the Royals.

On Saturday night, when the Mets had a chance to tie the series at 2-2, the team blew a 3-1 lead late.

With two on and two out in the eighth inning, Mets' second baseman Daniel Murphy had a ball roll under his glove for an error. It scored the tying run and enabled the Royals to plate two more for a 5-3 victory and take a commanding 3-1 lead in the series.

Familia, who dominated in the regular season with 43 saves and in the first two rounds of the playoffs, is the first pitcher in the majors with two blown saves in a World Series since the Philadelphia Phillies' Ryan Madson in 2008.

Think about it. If the Mets held on two both of those games, the Mets were in position to celebrate in Queens.

After all, they had Harvey going in what should have been a close out game.

Harvey showed and did ace-like work through the first eight innings, allowing no runs on four hits.

Then, everything fell apart.

The Mets didn't do a lot of damage with just two hits - a Curtis Granderson solo homer in the first inning against Royals' starter Edinson Volquez. The other Mets run was unearned.

To be fair, the Royals came back and took those games every time the Mets left the door open. The same thing was true on Sunday.

That's what good teams do; capitalize on other team's mistakes.

The Royals are truly the Comeback Kids. They are the first team to come back from at least two runs seven times in a postseason run, including in the World Series clinching game.

In this comeback, it was Lorenzo Cain who got it started with a leadoff walk against Harvey. Eric Homser followed with a double. He would score to tie the game on the bad throw error by Duda.

"The way it ended last year, with everything that happened, such a magical run, you knew it couldn't end like that again," said Hosmer, whose team lost to the San Francisco Giants in seven games in 2014 WS. "You knew that story had to have a way better ending than losing Game 7."

The Royals won this time. And the Mets lost - thanks to them.