It was four years ago Friday. It seems four centuries ago. Two minutes and 34 seconds before halftime in Super Bowl 51, Tom Brady threw one of the worst passes of his life.

It was third-and-6, his team already 14 points in arrears. He thought he had Danny Amendola, working one of those “rub” routes, one-on-one against Brian Poole. Brady didn’t see the lurking Robert Alford until the oft-penalized cornerback burst in front of Amendola and Poole. And here I turn it over to faithful reader David Johnson, who wrote last week:

“I think about Brady diving helplessly at the feet of Robert Alford. He looked so old and slow and finished.”

Indeed, Brady’s attempt to tackle Alford soon became an illustration in the O.E.D. under the word “pitiful.” (OK, I made that part up.) In some ways, he was way ahead of his team: In the putative effort to prevent a pick-6, Brady managed to keep what we now recognize as a social distance. Alford’s touchdown made the score 20-0. Fox cameras caught the Falcons’ brass celebrating wildly in the stands at NRG Stadium. Arthur Blank, the high-profile owner, was delivering a series of high fives.

In that moment, we felt – or thought we felt – tectonic plates shift. Brady and Brady’s imperial team looked like yesterday’s men. The Falcons, under a newish and energetic head coach and with a roster laden with fast and fierce players and their just-crowned MVP quarterback, appeared the new bosses on the NFL block.

How delicious the moment. How fleeting it was.

Here’s Mr. Johnson, again referencing Brady: “Instead he won that (Super Bowl) and has since been to three more. Unbelievable.”

Well, yes. But also no. For as much as we think we know about sports – and we sportswriters figure we know everything – we’re constantly reminded that, borrowing the William Goldman quote for the thousandth time, nobody knows anything. Two minutes before halftime on the night of Feb. 5, 2017, you’d have bet a lot of money that the Falcons of Dan Quinn would win not just that Super Bowl but a few more, and you’d have pronounced the Patriots dynasty at its arrogant end. Nope and nope. In sports, something always happens.

The Falcons fired Quinn last fall; he presided over one more playoff victory. He’s now the Dallas defensive coordinator. The team Quinn left to come here seemed destined to win multiple Super Bowls, but Malcolm Butler (and Brady, naturally) spoiled the Seahawks’ chances at a second in a row, and even Russell Wilson hasn’t gotten them back to the big game. Two years ago – yes, only two – the Rams of Sean McVay and Jared Goff and Todd Gurley were anointed the Next Big Thing. They lost the Super – to Brady, naturally – and have since fractured. Gurley played for the Falcons, to no great effect, this past season. Goff was just traded to Detroit for Matthew Stafford.

And Brady? He looked finished as he gazed dolefully downfield at the escaping Alford, finished again after throwing a game-ending Pick-6 against Tennessee in the wild-card round last season. Even after relocating to Tampa Bay, he had moments – the blowout losses to New Orleans, another wretched first half against the Falcons – when it was apparent he’d stayed too long at the fair. But here he is again, gracing a 10th Super Bowl over 19 healthy NFL seasons. Add Peyton Manning and Joe Montana, maybe the second- and third-best QBs ever, together, and toss in Aaron Rodgers and you don’t get 10 Super Bowl appearances.

This is the NFL, where everything changes, everything except the one big thing. Brady has made as many Super Bowls in his 40s – this is just nuts – as in his 20s. Now he has made one without Bill Belichick, without Robert Kraft, without any of those dastardly Patriots (except Gronk) to help with the lifting.

Me being a sportswriter and therefore knowing everything, this would be the moment to clear my throat and offer a proclamation as to What This All Means. Trouble is, I’m not sure what any of it means. I’m not sure why the Falcons, who outplayed the Patriots all ends up for 2½ quarters four years ago Friday, collapsed that night and spent much of the time thereafter collapsing on cue. I’m not sure why only one team – Brady’s Pats, naturally – have won consecutive Super Bowls this century. I’m not sure what happened to the Seahawks; I have no idea what went wrong with the Rams.

This Super Bowl is about Brady, yes, but it’s also about Patrick Mahomes and the Chiefs. They’re the defending champs. They’re favored again. Forced to choose, I’d pick them to win. I’d pick them to win for the next five years. That’s how unstoppable Mahomes and his receivers look. But Rodgers was 27 and similarly resplendent when he won his first Super Bowl; he’s 37, still waiting on a second.

For all its buttoned-down efficiency, the NFL can be weird. Every team starts every season asking, “How can we get to the Super Bowl?” and 30 of them fail. The only thing that doesn’t fail is having Tom Brady. At age 42, he switched cities, conferences and coaches. He turned 43 in August of a pandemic year. Here he is again.

And Robert Alford? The Falcons released him Feb. 5, 2019 – two years to the day after he flashed past Tom Brady. He signed with Arizona. Because of injuries, he hasn’t played in an NFL game since.