James DeGale climbed off the canvas in the final round to claim a majority draw against Badou Jack in their world super-middleweight unification title fight at the Barclays Center in New York.
IBF champion DeGale knocked down Jack in the opening round but the WBC titlist grew into the bout and finished the stronger of the two, flooring the Londoner, who got to his feet to hear the final bell.
The final knockdown proved decisive as DeGale was given the nod 114-112 on one of the judges' cards but the other two scored the contest 113-113, with both fighters keeping their titles after a thrilling night in Brooklyn.
DeGale's record now stands at 23 wins, one draw and one defeat from his 25 professional contests, and he revealed afterwards that the bout had taken its toll.
The 30-year-old told Sky Sports 1: "He busted my ear drum and I lost my teeth. I thought I'd done enough but it was the knockdown.
"I've had 25 fights, I'm going to get better, I want the rematch! I'm glad I'm still the champ and I'm coming home with the title but I'm so upset that I didn't come with the WBC belt.
"The main thing is I didn't lose, I'm still the champ and I can move forward."
DeGale became embroiled in an exchange with Floyd Mayweather, the former five-weight world champion and Jack's promoter who insisted the Las Vegas-based Swede deserved the decision.
With DeGale protesting in the background, Mayweather said: "This is bad for boxing when it's all said and done, this is really bad for boxing."
A rematch seems the most obvious solution after a sensational encounter, but Mayweather indicated Jack (20-1-3, 12 KO wins) intends to move up to the light-heavyweight division.
Mayweather said: "We don't need to figure it out, I'm the promoter this is my fighter. Badou Jack has got too big for 168lbs. We have plans after this fight to move up to light-heavyweight."
DeGale was fighting in North America for the fourth bout in a row, the first of which saw him claim the vacant IBF title with a unanimous decision win over Andre Dirrell.
He had followed it up with routine points victories over Lucian Bute in Quebec, Canada, and Rogelio 'Porky' Medina in Washington DC but seemed on course for his first stoppage in four fights when he knocked down Jack in the last 30 seconds of the opening round.
The 2008 Olympic gold medallist punctuated a cagey start with an overhand left that found Jack's chin and sent the 33-year-old flat on his back. Jack beat the count but that seemed to give his opponent plenty of confidence.
DeGale was the busier fighter over the next couple of rounds, with his superior footwork allowing him to dance in and out, and land some stinging shots in the process.
But DeGale showed signs of slowing down in the fourth and fifth, where the most notable action came after the bell when Jack accidentallyplanted a left hook on referee Arthur Mercante Jr, who was attempting to split the fighters.
Mercante Jr had to be momentarily held up by Jack, and the official admonished himself once he had regained his senses.
That did not distract Jack, who had his best round in the sixth, pinning his foe against the ropes and landing several heavy blows to the body and head before DeGale came firing back towards the end of the round.
But he was clearly still struggling as Jack, who was by now successfully cutting off the ring in an attempt to negate DeGale's footwork, landed an overhand right that buckled his fellow champion's legs momentarily.
DeGale was hurt again in the eighth following an overhand right and he was forced to retreat. Indeed the booming shot knocked out DeGale's mouthguard and may have been the moment he lost a tooth.
DeGale showed fighting heart to arguably shade the 10th and 11th rounds but Jack was showing no signs of fatiguing and set up an incredible finale by flooring DeGale in the opening minute of the 12th.
It was a big right hand that did the damage to send DeGale down to the canvas for the first time in his professional career but he got to his feet and finished strongly.
It mattered little as the round was a mandatory 10-8 for Jack. Had DeGale not been knocked down, he would have walked away with a unanimous decision victory.