Expected to be contenders in the National League, the Mets instead became one of the most disappointing teams in baseball, pulling into the All-Star break as a diminished version of themselves.

Injuries have ravaged the pitching staff, robbing it of ace Noah Syndergaard and closer Jeurys Familia. And those who have stayed healthy have been cursed by inconsistency.

“I really think you can point to the injuries,” rightfielder Jay Bruce said. “It’s tough when you’re fighting an uphill battle all the time. It’s tough when you’re trying to overcome it, and you’re trying to make sure that you don’t pay attention to it. You say it doesn’t matter, it doesn’t matter. But, it matters.”

As the Mets begin the season’s second half Friday against the Rockies, their slim chances of mounting a turnaround must begin with the same unit that has pushed them to the edge of irrelevance.

It is all about the pitching.

“There have been a lot of sleepless nights, a lot of sleepless nights,” said pitching coach Dan Warthen, who has presided over an uncharacteristic spike in walks and homers.

At 39-47, the Mets have only a 7.4-percent chance of making the postseason, according to FanGraphs. Friday begins a critical period leading up to July 31, not just the official deadline for nonwaiver trades but also an unofficial deadline to decide whether this season is a lost cause.

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“We saw a team that last year, when they were challenged, they rose up,” manager Terry Collins said. “That’s why I think it’s in their DNA that they can do it again. So, we’ll find out.”

But it will take something more than leaning on the past to reverse what has been a perfect storm of calamity. Without Syndergaard, the rotation lost a stabilizing force. His absence hurt more as Jacob deGrom spent much of the first half looking to regain his familiar form. But by the time he hit his groove in mid-June, the damage had been done.

The weakened rotation exposed a bullpen that began the season with little margin for error. Familia’s surgery to repair a blood clot pushed it to a breaking point. Addison Reed successfully took over for Familia, though the other relievers have struggled in new roles.

A year ago, Fernando Salas solidified the bridge to Familia. This year, his ERA has skyrocketed to 6.44, as he seemingly has been unable to bounce back from a heavy early-season workload. Hansel Robles’ sudden loss of command led to a 6.23 ERA and a demotion to Triple-A Las Vegas, where he hasn’t done much to warrant a second chance.

The deterioration of the pitching amplified another uncomfortable reality: a porous infield defense that increased pressure on pitchers.

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“We haven’t played the baseball we expected coming out of spring training, and it’s not only one area,” said Jose Reyes, who was moved from third base to shortstop as an attempt to shore up a leaky defense.

The Mets have converted only 68.3 percent of batted balls into outs, tied for the lowest mark in baseball.

“We ended up trying to be too precise and walking people, getting behind, starting to pitch away from contact,” Warthen said. “We’ve had a lot of new faces, and a lot of young guys who have a history of walking people.”

Syndergaard and Familia are expected back this season, as is Matt Harvey, who has been a shell of himself following surgery for thoracic outlet syndrome.

But as the Mets emerge from the break, they are greeted with opportunity, with series against the Rockies, Cardinals, A’s, Padres and Mariners leading up to the deadline.

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“We have enough games with the people that we have to beat that yeah, I think we can get back into this thing,” Warthen said. “But we certainly have to pitch better and play better.”