It was a viral video before there were viral videos. A TikTok before Tiktok.

I'm referring to the video of Diego Maradona's warm-up routine ahead of Napoli's UEFA Cup semifinal second leg against Bayern Munich in 1989, which happened 31 years ago on Sunday.

In an era of slick viral videos, athletes doing keepy-ups on camera or influencers recreating classic soccer moments in their gardens, Maradona's old footage still reigns supreme.

It's probably the most-watched bit of organic on-pitch football footage that doesn't include a second of game action. It's both of its time and ahead of its time. It's a Pieter Bruegel painting in the sense that there is tons going on, except it all revolves around one figure: Maradona.

Forget your feelings about the man. Forget what you know and what you've seen, like Asif Kapadia's excellent documentary. Come at this footage fresh and ask yourself: what is going on? What am I watching?

You know it's not the present because of the old-school signage for brands that were once household names, like AGFA, who made film for cameras, and Commodore, the computer company that went bust more than a quarter of a century ago. And, of course, the crowd behind is blurry: still intelligible, but not defined to the standards of our HD era. Napoli's warm-up gear is decidedly old school. Brands like Mars don't sponsor clubs these days, and nobody wears those baggy tops.

But look closer. Maradona is wearing his top differently. It looks like he's taken a spare set of shoelaces and cinched them around his waist like a make-shift belt.

The music starts -- "Live is Life," by Opus -- and he starts to shimmy. For a moment, Antonio Careca, his strike partner at Napoli, does too. You expect that from Careca: he's Brazilian. But then he stops and keeps stretching, which is also not surprising. A bit of fun, a bit of flash for the cameras and then off to work.

Not so for Diego; this is where the show begins. He starts juggling the ball and then there's a sharp cut to a close-up that confirms what you may have noticed before: his shoelaces -- the ones around his boots, not the ones around his waist -- are untied and hanging loose. Why? Cicco Marolda, who covered his entire stint at Napoli for the local newspaper, "Il Mattino," explains that Maradona "always trained with his laces undone. He just felt more comfortable that way, he felt the ball better. He'd only tie them up just before kick off."

Next, he's pogoing up and down with the ball seemingly stuck to his head. From there, he's juggling with his knees in time with the music. Then it's back to his head as he walks nonchalantly with the ball nestled in his thick, black hair. Off it goes next to his foot, where it stops dead, as if stuck to a magnet. And he's off again, juggling: foot, shoulder, head, faster and faster as the chorus picks up.

Another sharp video cut and Maradona's now clapping. He knows he's being watched and he knows he's the center of attention, but he never looks to the crowd. In fact, he stops and the next thing you see is him standing still, possibly stretching his lower limbs while jiggling his hips in time with the music. His expression, which had been calm, almost child-like, slips into game face.

He bounces back and forth, feet together and he's off again. Juggling the ball as if held by an invisible string, tempo picking up, Diego jumping with it, foot to head to shoulder, all in time, all in uncanny control.

At one point, you see his teammates, dutifully jogging past, performing drills while he performs art. Only at the very end does he crouch to stretch with them before emerging from his squat with a cry that goes unheard against the musical backdrop. Those in the stands know they've seen something they'll be telling their grandkids about.

Marolda, who was sitting in the press box at Munich's old Olympiastadion, recalls being transfixed. Even after six years of covering each and every Napoli match and training session, he had seen nothing like it.

"It was unusual to begin with for Napoli to warm up on the pitch. In those days, it took place before the teams came out," he says. "We didn't really pay attention until the music started. Within seconds, everybody was watching. Nobody wanted to miss a thing."

In fact, nobody except the 70,000 there that day would have seen it if it hadn't been for a Belgian TV producer named Frank Raes. The cameras were filming, but none of it was being aired except on the stadium's JumboTron. Raes realized the enormity of what he had just witnessed. He contacted the German broadcaster ZDF, who provided the production crew, and they sent him 12 minutes of pre-match footage. He cut it together to make the video that was first shown on Belgian TV and has now achieved YouTube immortality. ("If I had a penny for every time that video gets played, I'd have long retired to Hawaii," he joked recently.)

The spontaneity of it all is a big part of its popularity. It feels organic and, in fact, it is, right down to the fact that the music wasn't played by some DJ, but by a cover band that churned out a a range of early 1980s hits, including Opus.

The warm-up by Maradona that day reeked of nonchalance. Maybe some arrogance, too. This was his biggest game to date in club football -- Napoli were 2-0 up on Bayern after the first leg, but nothing was guaranteed away from home in those days -- and this was how he approached it.

There's an Italian word for it: "sprezzatura." These days, you'll hear it mostly in men's fashion, referring to "the ability to look stylish while appearing to do so without the slightest bit of effort" (when, in fact, there's often plenty that goes into it). But it was first defined way back in 1528 in "The Book of the Courtier" as the ability "to accomplish difficult actions [while hiding] the conscious effort that went into them." In this case, Maradona's act hits both the modern definition (the "studied carelessness" of his unlaced boots and makeshift belt) and the medieval one.

Much has been written about the psychological effect Maradona's warm-up had on the Bayern players, who were busy going through their paces on the other side of the pitch. Some did stop to stare, while others looked on out of the corner of their eyes.

It even clouded memories. Jurgen Klinsmann recalled the day, saying: "We're on the other side of the field, warming up like Germans: seriously focused... there's music playing, the song 'Live is life' and to the rhythm of the song, Maradona started juggling the ball. So we stopped our warm-up... and we couldn't warm up anymore because we had to watch the guy."

Except, of course, Klinsmann wasn't actually there. He wasn't playing for Bayern at the time -- he was at Stuttgart, who would lose the final over two legs to Napoli. The fact that it made such a lasting impression in the former USMNT coach's brain, creating a false memory, tells you plenty about the impact it had.