First middleweight champion Anderson Silva lost his title, caught clowning once too often in the cage. And on Saturday, light-heavyweight title-holder Jon (Bones) Jones — his successor as the top pound-for-pound fighter on the planet — was pushed to the limit by 8-1 underdog Alexander (The Mauler) Gustafsson at UFC 165.
Some fear that welterweight champ Georges St-Pierre, currently No. 2 in the pound-for-pound rankings, could also be in a long — or short —night in November when he faces top 170-pound contender Johny (Bigg Rigg) Hendricks, a former NCAA champion wrestler with a sledgehammer for a left hand, at UFC 167.
Such is the beauty of mixed martial arts, where there are so many ways to win and lose. And champions wear the biggest targets on their back.
There was little beauty in Saturday's main event, other than marvelling at the amount of punishment two superbly conditioned and trained athletes can absorb.
It was like watching a time-lapse video of two bodies breaking down. Fascinating but brutal.
Jones rallied to win a stirring five-round decision, with the judges scoring it 48-47, 48-47 and 49-46 for the champion.
A busted-up Jones had to plead with the ringside physician not to stop the fight after four rounds, according to UFC president Dana White.
Most gave Jones either rounds two or three plus four and five.
Neither fighter made it to the post-fight news conference at the Air Canada Centre. Both went straight to hospital, with Jones bundled directly onto a waiting gurney.
The two had been released come mid-morning Sunday, with the challenger leaving ahead of the champion.
Both men looked like they had been in an accident as they waited for the result to be announced after 25 action-packed minutes. They could hardly stand up.
Gustafsson had a bloody ear, a contusion under the eye and a glob of Vaseline on top of a cut high on his temple. Jones had a bandage above his right eye, mouses below both eyes and his post-fight speech came through bloody, swollen lips.
"Not that I can talk to this either, but I believe that this is one of those fights where both guys felt like they were going to die," White told reporters after. "You feel like 'I don't know if I can continue, I don't know if I can keep doing this, I don't know if I've got one more round in me.' If they even knew what round it was. One of those kind of fights.
"It's why you have to respect what happened here tonight so much."
Critics will point to the fight as everything that is bad about the sport. Fans will talk about it for years, debating whether the challenger actually won.
Chances are the UFC will look to profit from a rematch.
Brazilian bruiser Glover Teixeira (22-2) is officially in the on-deck circle for the next 205-pound title fight, but the No. 2 contender may agree to wait his turn, knowing that another sapping Jones-Gustafsson donneybrook might aid his chances when he eventually fights the winner.
At six foot five, Gustafsson is one inch taller than Jones. And his 81.5-inch reach is only three inches less than the champion's UFC-leading wingspan.
Still few gave him much of a chance against Jones, who has fought a "murderers' row" of opponents in recent years, according to White.
Jones' five previous title defences came against four former champions and Chael Sonnen, who has fought for both the middleweight and light-heavyweight belts.
You can argue that most were on the downward side of their career but still his dance card was stacked.
Prior to Saturday, Jones had lost just one round in his 13-fight UFC career. And he had never been knocked down or taken down. His one loss in 2009 was in reality a win — he was disqualified for a downward elbow strike after leaving Matt Hamill broken on the canvas.
Hamill needed shoulder surgery. Brandon (The Truth) Vera needed facial reconstruction from Jones' ground-and-pound.
Gustafsson wasted little time going off script for a Jones fight. He cut the champion in the first round and then dumped him on his back. It soon became clear that he had the faster hands.
Jones fought back with kicks and elbows, but Gustafsson continued to score with strikes. By the fourth round, Jones' face was showing real damage.
But a spinning elbow late in the round dazed Gustafsson and Jones pressed his advantage with knees. That set the stage for a wild final round, with Jones getting the best of it against an exhausted opponent.
Jones led Gustafsson 134-110 in total significant strikes. The champion targeted the legs, landing 53 strikes there to the challenger's 15.
According to FightMetric, Jones outstruck Gustafsson in every round but the fifth when the count was tied at 24-24. The champion led 28-19, 26-15, 29-26 and 27-26 in the other four rounds.
The Swede was 1-for-8 on takedowns, marking the first time Jones had been taken down in his UFC career. Jones, a former junior college wrestling champion who had landed 61.9 per cent of his previous UFC takedown attempts, was 1-for-11 for a success rate of nine per cent on the night.
Gustafsson's wrestling defence was razor-sharp, thanks no doubt to his work with former NCAA wrestling champion Phil (Mr. Wonderful) Davis. After being outwrestled by Davis in 2010 in the lone loss of his career, the Swede started training with him at Alliance MMA in San Diego.
The Swede has now defended 26 of the 30 takedown attempts he has faced in the UFC.
For Jones, the win adds to his legacy, and speaks volumes about his character and guts. But it also shows he is human.
"He definitely looked human tonight," said White. "But it takes a superhuman on both sides to do what they did tonight for five rounds, just pounding each other — and to keep going.
Jones (19-1) joins Anderson Silva, GSP and Royce Gracie as the only fighters in UFC history to post 10 straight wins.
The win also gives Jones the record for most consecutive title defences (six) in UFC light-heavyweight history. He already holds the mark for most submissions (five) by a light-heavyweight and is tied for most finishes (nine).
"Tonight was a blessing in so many ways," Jones said in the cage. "I got the victory and I got to prove a lot to myself. I'm not satisfied. I have to do a lot more in the gym to stay on top of my game."
"Team Jones, we're still here, baby," he added. "It's a beautiful night for me."
A supremely confident Gustafsson (15-2) had promised to shock the world. And while he didn't win the belt, the classy Swede did shock the MMA world.
"It was one of those exciting, great fights because it was what nobody expected," said White. "Things happen that you did not expect to happen. And when that happens, it freaks you out, you go crazy."
"This was one of those fights tonight that you remember why you're a fight fan," he added.
Or why you're not.