NEW YORK – What is the Mets’ biggest problem as they fight for a spot in the postseason? Throwing strikes. After Thursday’s 7-6 loss to the Athletics at Citi Field, New York’s pitching staff leads the National League in walks with 468. That’s only 17 walks fewer than the Major League lead held by the White Sox.

Manager Carlos Mendoza used six pitchers -- Jose Quintana, Reed Garrett, Huascar Brazobán, Phil Maton, Ryan Stanek and Edwin Díaz -- in the game, and most of them couldn’t find the plate well, walking a combined 11 batters. Mendoza’s voice told the entire story: He is not pleased that free passes have been a prominent issue for most of the season.

“We need to dig deep and see what’s going on here,” Mendoza said. “Obviously, when we struggle early in the year, [it’s] the free passes. Too many non-competitive pitches. Today was not a good day. We saw it from the beginning. … It’s hard to win a baseball game when you allow 11 walks.”

At first, it looked like the game was going to be a walk in the park for the Mets. They jumped out to a 5-0 lead after three innings. Mark Vientos highlighted the early scoring with his first of two homers in the game. However, New York didn’t score again after the Vientos homer in the fourth, which made it a 6-4 game.

Of the 11 walks New York allowed, three of them scored -- including two issued by Quintana in the fourth on a grand slam by JJ Bleday, who made it a one-run game.

“It was a rough inning,” Quintana said. “They gave me an opportunity to win this game, and I couldn’t make it.”

Quintana had problems throughout the game. Before the dreaded fourth, Oakland loaded the bases twice, but Quintana managed to get out of the frames. Only the second inning was stress-free because he retired the side.

Once Quintana left the game after four innings, the A’s trimmed their deficit to 6-5 in the fifth when Brazobán threw a wild pitch, scoring Zack Gelof. The sixth inning belonged to Reed Garrett, who allowed two runs to score to give Oakland the lead.

The Athletics ended up taking two out of three games in the series, and the Mets are now two games behind the Braves for the third and final National League Wild Card spot. There is a state of urgency to start throwing strikes and giving the team a chance to gain ground in the standings.

“When you have an opportunity to win a series on a day like today,” Mendoza said, “when you take a lead, [then] you let them right back in the game and you end up losing the series -- especially where we are at -- you talk about having a sense of urgency. We just didn’t get the job done today. We just have to turn the page and get ready for the Marlins series.”

Designated hitter J.D. Martinez said the players recently talked about staying positive despite the problems they have had in recent days.

“Today was one of those days where we started off good, and they kind of just rallied back,” Martinez said. “It was tough to score off [closer Mason Miller]. He’s got a good arm, so it’s one of those things where we turn the page and come back tomorrow.”