This was the big sports event of the weekend.

UFC 193 and the knockout defeat of Ronda Rousey in Australia on Sunday by fellow American Holly Holm.

In case you missed it, here are the dozen seconds or so that ended the fight — with Rousey on the canvas, bloodied and concussed.

Something an observer learns, when following any of the combat sports and, for most of my life, that meant boxing …

Any time a champion begins to believe his or her own hype … they are in trouble.

Ronda Rousey just found that out.

After all of 12 fights (12, total) … she allowed the UFC-stoked publicity machine to run away with glowing/fawning descriptions of her mastery of her sport.

A month ago she said: “It’s not about the individual girls or the individual matches anymore,” she said. “I want to be remembered for the greatest that ever did this sport and to retire undefeated.”

She earlier had called herself “the greatest ever” and had confided that she was considering a break from fighting to work on her film career.

After 12 fights.

A fighter who allows themselves to get distracted by non-fighting goals and admits to thinking about goals beyond the next fight … is someone headed for a fall. Whether it is Mike Tyson, ahead of Buster Douglas knocking him out, or a thousand other athletes far more accomplished than Ronda Rousey, ahead of their first defeat.

(More on Iron Mike: He won his first 37 fights, taking away pieces of heavyweight titles from four serious heavyweights, Michael Spinks, Trevor Berbick, James Smith and Tony Tucker, and also beat Frank Bruno, Tyrell Biggs, Pinklon Thomas …)

Let’s stipulate that the competition for the UFC’s bantamweight title probably is not particularly deep. Seem fair?

How many women are doing mixed martial arts? How many are bantamweights? How many of them are serious about it? One hundred? Fewer?

When the level of competition is thin and the competence of that handful is uneven, and mostly even less experienced than Rousey, one person might get the impression she is unbeatable. Maybe even “the greatest female athlete ever” — as chosen by ESPN earlier this year. (Which is ridiculous. Hello, Serena Williams? Jackie Joyner-Kersee? Mia Hamm? Martina Navratilova?)

What happened in that fight was fairly simple, and really makes a person wonder about the idiocy of those who were flocking to praise Rousey on the basis of such a short career.

Rousey met up with Holm, a former boxer and kick-boxer with far more ring experience, including 38 boxing matches and 10 MMA bouts. And Holm beat the hell out of her.

Part of solving the “unbeaten champion” for a challenger is remembering that no one is unbeatable. No one. A handful of fighters (Rocky Marciano) get out before they lose, but nearly everyone else (and Floyd Mayweather may be risking his legacy here) goes down.

And if the fighter can enter the ring believing he or she can win, the chances of doing just that skyrocket.

Holm seemed to appreciate that. She didn’t seem beaten before the fight even began. Perhaps because she had the perfect skill set to combat Rousey.

Rousey came out of judo, and she wants to take everyone to the mat and win with an armbar. She had done just that in nine of her 12 victories. A one-trick pony.

Clearly, the way to deal with her was to stay upright, and box.

Holm was good enough at that in the first round to bloody Rousey’s nose and leave the rest of her face red from the blows. (Unbeaten champions hate seeing their own blood, and they often seem to panic and make ever more mistakes.)

In the second round, Holm hit Rousey on the jaw with a left hand, staggering Rousey, who fought to regain her balance, only for Holm to kick her with a left foot that hit Rousey in the throat and dropped her like a bad habit.

That’s how unbeaten champions lose. They get arrogant, they get distracted and maybe they can’t be bothered to take an opponent seriously.

To see a version of the fight that is even more telling than the video, check this photo gallery. It shows the damage the women were doing to each other but, especially, what Holm was doing to Rousey.

Photo No. 3 shows the kick that ended it. Photos 4 and 7 appear to be the left hand that set up the decisive kick.

Going forward, let’s hope, again, that we don’t lose our minds over someone who wins their first 12 … anything. That’s far too small a sample to prove anything. Just because modern social media tends to let reputations ran far ahead of reality doesn’t mean the serious fans have to be sucked in by it.