PHOENIX — The extreme underdog Diamondbacks pulled off yet another miracle in a season of them late Friday, and if this keeps up, they might rival the 1969 Mets in baseball’s annals of the Amazin’.

The D’backs’ Cinderella story deserves and will get a couple of more chapters after they engineered the most stunning win yet in their shocking season.

Before a packed and raucous sellout crowd at Chase Field, Arizona’s resilient team came back late from a three-run deficit to beat the powerful and star-packed Phillies, 6-5, and give themselves a real chance to pull off the upset of this October. The young, upstart squad that never quits tied up a National League Championship Series that was supposed to be over by now, but will at least return to Citizens Bank Park in Philly now for a sixth game — and maybe a seventh.

The team that was picked to finish fourth in the NL West is now two games from the World Series. Which surprises all of us so-called experts.

“I don’t think anybody’s surprised in here,” Diamondbacks veteran Evan Longoria said. “Good thing about the teams that are counted out — it makes you stronger.”

“Everyone in here expected us to excel,” said ace pitcher Zac Gallen, who starts in Game 5 here Saturday night. “Guys have that little bit of chip on their shoulder. We’re better than people gave us credit for.”

The Diamondbacks, who already have advanced three rounds beyond their preseason expectation, victimized the Phillies’ two best relievers late, overcoming a three-run deficit to win 6-5 and even the NLCS as two games apiece. Alek Thomas smashed a two-run home run in the eighth inning off Cooperstown candidate Craig Kimbrel and Gabriel Moreno lashed a run-scoring, game-winning double off Jose Alvarado, the Phillies’ best reliever.

“We’re not done yet,” Thomas said over the loudspeaker.

If they win six more games, they should surpass the 2006 Cardinals and 1988 Dodgers in a competition for most surprising champion. It’s tough to top the Amazin’ Mets, but then, even Arizona’s 84 regular-season wins were seen as a beacon of overachievement.

If Arizona can somehow win two of the next three games, it will become that rare 84-win team to reach the World Series, joining the 1973 Mets (83 wins actually) and 2006 Cardinals (84 exactly). Gallen smiled at the ’69 Mets comparison, noting his announcer when he played in New Orleans was Ron Swoboda.

For the first two games at least, the Phillies could do no wrong. And nearly everyone except the Diamondbacks themselves was starting to give up on them. That includes some of their fans. Internet prices for “get in” tickets for Game 4 dropped about 90 percent from around $100 to around $9.

Who could blame them? The Phillies certainly appeared unstoppable after they won Game 2 by a 10-0 score and eventually pushed their postseason ledger in home runs to 20-4 over their opposition, which also included in the wild-card round the Marlins, who actually won more regular-season games than Arizona. But while the Marlins have been busy firing or forcing out some of their key decisionmakers, the Diamondbacks are staging a party out here.

The story just keeps getting better by the day.

The Phillies stand with the fourth-highest payroll and a collection of stars, both position players and rotation stalwarts, making them an obvious and overwhelming favorite in this series even before it began. And get this: their stars have played exceptionally well, from Zack Wheeler to Aaron Nola to Bryce Harper to Trea Turner. But it may not be enough.

Could the stars actually be aligning for the Diamondbacks? It was a positive sign when Turner, who stole about a million bases in a row, was picked off by Joe Mantiply in the first inning — the reliever’s only inning as the opener in a bullpen game that worked for Arizona.

The Diamondbacks, picked by almost everyone to finish fourth in the NL West (below the Padres and Giants as well as their forever nemesis Dodgers), do the little things. Which is great because they don’t do a lot of big things.

It’s tough to explain how they got to Game 5 despite struggling to score runs until their final (eighth) inning last night. Really, their whole year is.

Another surprise: It’s pretty darned loud at Chase Field. While they may not match the crazed fans in Philly, they raised their own roof. Some Phillies fans were said to have been stocking up on those $9 and $10 tickets without any intention to attend but just to lower the decibel level. (Now those are some real fans!)

In any case, the energy here is impressive considering everyone has to be hot. The fans seem pretty stoked at having an opportunity to return to the World Series for the first time since 2001, when Randy Johnson, Curt Schilling and a very veteran team beat the Yankees in one of the best World Series this generation.

This is a very different kind of Diamondbacks team. But right now, it looks pretty darned dangerous.