TORONTO – Seconds after he had retained his light heavyweight title Saturday at the Air Canada Centre by the narrowest of margins over Alex Gustafsson, Jon Jones was lying on a stretcher, headed to a local hospital.

He'd left every last ounce of energy he had in the cage, and had no more to give when the final bell sounded to end his epic battle with Gustafsson in the main event of UFC 165.

Question, if you want, whether Jones deserved to win the fight. It was close, and could have easily gone Gustafsson's way.

Question, too, perhaps, the media for deifying Jones far too early in his career.

But question Jones' toughness, fortitude and willingness to win at your own risk. You'll look like a fool if you do, because Jones proved his mettle beyond a doubt in a match where he had to do something big in the final two rounds and did just that under extremely adverse conditions.

Judges Richard Bertrand and Doug Crosby scored the bout 48-47; Chris Lee had it 49-46 for Jones, who was in more danger on Saturday than he had been in his six previous championship fights combined. Yahoo Sports also saw it 48-47 for Jones, giving him Rounds 2, 4 and 5 while scoring Rounds 1 and 3 for Gustafsson.

Jones pleaded with the ringside doctor after the fourth round not to stop the fight because of a large cut above his right eye that sent gushes of blood streaming down his face and blurring his vision.

The final round was an epic battle, with both men so worn that in the final moments, they could barely breathe and had to bend over to catch their breath a second before resuming the attack.

Gustafsson, who entered as a massive 8-1 underdog, stunned Jones in many ways. He became the first man in the UFC to take Jones down and largely neutralized Jones' wrestling. Jones' secret in his career to this point had been to keep fighters at a distance, and then ultimately take them down and open them up with big elbows.

This time, though, he wasn't able to peck away from the outside – that advantage Saturday clearly went to Gustafsson – and he couldn't get the Swede onto his back as he had so often done in previous title fights. Jones didn't get a takedown until late in the contest and it was, as it played out, essentially meaningless.

Jones had to summon his inner strength to fight his way back into a bout that he clearly seemed to be losing at its midpoint. Late in the fourth round, Jones landed two vicious spinning elbows, as well as a couple of kicks and a flurry of punches, sending Gustafsson wobbling back to his corner.

Gustafsson recovered remarkably between rounds, but Jones managed to carry the fight to him in the fifth. It was a case of Jones raising his game because Gustafsson forced him to do so.

The crowd of 15,504 was roaring its approval as the fourth rounded ended and didn't sit much during the rest period. It remained on its feet for a large portion of the final round, with the cheers building to a crescendo in the closing seconds.

"It was a great fight, and it was one of those exciting, great fights because [what happened] is what nobody expected [to happen]," UFC president Dana White said. "Things happened that you did not expect to happen. When it does, it freaks you out and you go crazy. … This is one of those fights tonight that you remember why you're a fight fan and why you love fights so much. When a round ends and the whole place is on its feet with a standing ovation, and they did that for all five rounds, it's amazing. I love being a part of things like this."

Gustafsson was masterful and it looked for a long time as if he'd pull off one of the most shocking upsets in the 20-year history of the UFC.

He took Jones apart while they were standing, clipping him with a series of shots.

It was gut-wrenching to see Gustafsson pacing the cage, eyes fixed on the floor, in the seconds after the decision was announced. He, too, had pushed himself far beyond what his limits seemed to be to go just a bit longer, just a bit harder.

Gustafsson's toughness, though, had never been in question. There was a small but vocal segment of the audience which, perhaps jealous of Jones' dominance, questioned his toughness and belittled his achievements.

Jones, meanwhile. may not have made any new fans on this night, but he willed himself to a victory when he seemed destined to lose.

"He definitely looked human tonight," White said of Jones. "He looked human tonight, but it takes a super human on both sides to do what they did for five rounds, just pounding each other and to keep going like they did. The doctor wanted to stop the fight and Jones pleaded with him not to stop the fight.

"He wanted that fifth round and went out there and performed the way that he did. Then, literally, he walked straight out of the Octagon into an ambulance."

There may be an immediate rematch, though White wouldn't commit to it. Really, he couldn't. The fighters were far too banged up to even think of the future.

"Jon Jones isn't even going to want to hear the word fight for two or three weeks, I guarantee you," White said.

Whether the UFC opts to pair Jones and Gustafsson again the next time out or to give Glover Teixeira his long-overdue chance doesn't matter.

The questions – if there ever really were any legitimate questions about Jones' toughness, fortitude and desire – were answered in front of more than 15,000 delirious fans on Saturday.

Jon Jones may not be able to walk on water, but there aren't any tougher men walking this planet than the UFC light heavyweight champion.