The Jets’ Defense has not yet lived up to its biggest challenges.

Its ability to reverse that trend will likely be the biggest determinant of the Jets’ chances to claw their way into the playoffs.

A true test of any NFL defense is how it performs against the league’s top offenses and quarterbacks.

The best defenses separate themselves by rising to the occasion and elevating against them, stifling offensive units that most others can’t.

The Jets went out of their way this offseason to share their belief that they have the best unit in the league.

There was D.J. Reed comparing the Jets’ defense to the 1986 Bears as historically great.

There was the bravado from John Franklin-Myers and Jermaine Johnson just before the start of the regular season, telling The Post the Jets had the best pass rush in the league.

There was Robert Saleh constantly telling reporters the Jets’ defense “comes in waves” every chance he got throughout the summer.

But how much of that confidence is based on performances against bottom-dwelling offenses and quarterbacks?

Dating back to last year, the Jets’ lauded defense has more often than not come up short when matched up against the league’s elite. It was glaring during the team’s 30-10 loss to the Cowboys at AT&T Stadium on Sunday.

“It’s one game,” head coach Robert Saleh said on a Zoom call Monday afternoon. “I don’t really think it really defines who we are as a defense, who we are as a team.”

Except, it’s not only one game.

It’s become thematic.

Last year, the Jets’ defense surrendered 27 points to Joe Burrow’s Bengals, 27 to Kirk Cousins’ Vikings, 24 to Lamar Jackson’s Ravens and 23 to Geno Smith’s Seahawks.

Other than 30 points allowed to Jacoby Brissett’s Browns, they marked the four-highest scores the Jets allowed last year.

Not so coincidentally, the Cowboys’, Bengals’, Vikings’ and Seahawks’ offenses all ranked in the top-10 highest-scoring in the NFL last year and top-15 in most passing yards, while the Ravens had one of the best rushing attacks.

The opposing quarterbacks and teams in the Jets’ four games with the least points surrendered?

Brett Rypien’s Broncos, Trevor Siemian’s Bears, Mac Jones’ Patriots and Aaron Rodgers’ Packers.

It’s become increasingly clear — the Jets feast against lowly quarterbacks and offenses, but when they’re needed most against the best, they keep coming up small.

“There’s always [another] level [we can reach],” inside linebacker and team captain C.J. Mosley said. “We never want to discredit ourselves. [The Cowboys] did a really good job of keeping us on the field. … When you have an offense, or really any offense like that that has that much time on the field, at some point something is gonna happen.”

The one elite offense the Jets’ defense has been able to figure out is the Bills, allowing just 16, 17 and 20 points in the three matchups last year and this year.

The Jets forced four turnovers in their 22-16 Week 1 win over Buffalo.

With Rodgers sidelined after his torn Achilles and Zach Wilson back as the starting quarterback, defensive dominance now provides the Jets’ most straightforward blueprint to victory.

Though Mosley praised his defense for limiting big plays by the Cowboys, the Jets were unable to bother quarterback Dak Prescott and capture needed third-down stops to get the ball back to the offense.

It was seemingly low tide for the Jets’ “we come in waves” pass rush, as they recorded just one sack and four quarterback hits.

Prescott carved up the Jets through the air, completing 31 of 38 passes for 255 yards, two touchdowns and no interceptions.

Receiver CeeDee Lamb dominated with 11 catches for 143 yards, lining up in different spots throughout the game to match up with different defensive backs in the Jets’ proud secondary.

The Jets failed to force any turnovers.

Dallas converted a whopping 9 of 18 third downs, helping the Cowboys have a 42 minutes 15 seconds time of possession compared to the Jets’ 17:45.

The third-down woes were the biggest difference from the Jets’ defense against the Bills to the showing against the Cowboys.

Now, the Jets must find a way to replicate their success against the Bills with the other top offenses they will face.

Their season depends on it.

“For us as a defense, we either have to cause a turnover, create a turnover, or get off the field on third down,” Mosley said. “I think that comes back to us executing more, being more consistent as a defense, and just trying to get off the field. Some of those plays they made, but a lot of them were on us as well.”