PHILADELPHIA — By now we know the Yankees’ mistakes without even googling them.

There was Frankie Montas, who had a hint of an arm issue in Oakland. Then he became a Yankee, and the issue defined him.

There was Josh Donaldson, who was whisked out of Minnesota because they didn’t like him there, and also because he was too pricey for the Twin Cities, either one of them. By the time he got to New York, he also lost his MVP form.

There was Isiah Kiner-Falefa, very versatile and a prince of a guy but not a true Yankee shortstop. Before that was Joey Gallo, who Yankees analytics people loved because of his high WAR. Of course, that number said nothing about whether he could survive New York.

Those unforced errors have been filling the pages of The Post (and whatever other papers still cover local teams in New York). But those are merely the mistakes of commission.

Quite likely, there were also a few of omission.

Rangers shortstop Corey Seager, an AL MVP candidate and one of the best left-handed bats in baseball, who led his team into the ALCS, might be one who got away as a free agent. But so might Phillies star Bryce Harper, who’s posting a 1.380 postseason OPS heading into the National League Championship Series that begins Monday night against the Diamondbacks.

Harper (1.011 OPS, 181 plate appearances) has the fifth-best all-time OPS for those with 150 postseason plate appearances, trailing Lou Gehrig (1.214, 150), Babe Ruth (1.214, 167), George Brett (1.023, 184), and Carlos Beltran (1.021, 215).

“He’s made for these moments,” Trea Turner, his teammate in Philly and in DC, said of Harper.

Philly feels right for Harper. The fans are gritty, emotional, into it — just like him. But New York would have worked nicely, too.

Harper’s camp tried hard to get the Yankees involved in free agency, and not just because they had the most money at the time. Harper’s dad Ron grew up a Yankees fan and Bryce wore No. 34 to honor Mickey Mantle, who wore 7. Three plus four, get it.

The sides talked a lot but the Yankees didn’t see the fit; they already employed Giancarlo Stanton (and of course Aaron Judge). Agent Scott Boras tried to sell them on Harper’s athleticism and ability to play first base, which he’s proving now. No go.

A case could also be made the Yankees shouldn’t have jumped at Stanton (I’ll save that for debate another time), and waited instead for Harper. Harper’s left-handedness made him a fit for the Yankees, but his lust for the limelight made him a natural for New York.

“Harper was built for major markets, pressure situations and big games,” Boras said. “He has an innate will and drive, a fearlessness of the opposition and the rare skill to provide confidence that overcomes temporary fear of failure. Yet when I told teams this they viewed it as hyperbole and noted he had a poor WAR value the prior season.”

Harper is a baseball lifer committed to his team, and to winning. He shouldn’t be defined by one analytic. But that mundane 1.8 WAR in 2018 did weigh, and so Harper had a tough time that winter (by superstar standards). He didn’t sign until spring training beckoned.

And while he received the biggest contract ever at the time — $330 million — he became an all-time bargain. The deal is over 13 years, meaning Harper makes “only” about $25 million a year. And because he’s committed to his team, he insisted on not including an opt-out even though Boras basically invented the opt-out.

Phillies owner John Middleton — who jetted out to meet Harper in Las Vegas twice — showed how committed he was to the pursuit, and Harper repaid that commitment. Perhaps he could have gotten another $300-million deal like Manny Machado had he consented to that opt-out, but he has a streak of stability it turns out. Word is Harper didn’t originally love the idea of going to a rival of his longtime Nats team, but after a winter of talks he was sold on being a Philly lifer.

The Phillies heavily considered Machado, but perhaps fortuitously, Machado signed his big deal first. Just as San Diego was a nice fit for Machado’s relatively mild public persona, Philly is where Harper belongs. He brings the grit.

It wasn’t a smooth ride to the finish line, however. Talks actually broke off for a day when Harper’s camp balked at $330 million for 15 years, and the Phillies thought he was gone to San Francisco or somewhere else before then-GM Matt Klentak resuscitated talks with a call to Boras.

Thanks to all the Phillies’ efforts, Harper warmed to Philly. They loved their sports, and their sports heroes, he remembered, and was reminded. Turns out Harper is the perfect player for this town. It all makes sense now.

The Dodgers floated the idea of a record salary on a deal about $160 million over four years. But Harper wanted to sign for life, and he did that with the Phillies, securing one of the first contracts that lasts practically until middle age.

The Phillies and Rangers are showing great teams can be built via checkbook, if correct calls are made. Meantime, the team in The Bronx, never reached for theirs. Atta boy, Yankees.