Ricky Hatton dredged up a performance full of guts and grit to claim the WBA welterweight title from Luis Collazo in Boston then admitted: "That was the toughest fight of my life."
Hatton earned a 115-112 (twice) 114-113 verdict over the awkward New York-based fighter, who almost had the Manchester 'Hit Man' out on his feet in the final round of a gruelling contest.
Even the great Kostya Tszyu had failed to put Hatton in as much trouble as Collazo, a 25-year-old who was well regarded for his slippery southpaw skills but boasted little reputation for power.
Such a major test was the last thing on Hatton's mind when he floored the champion with a left hand in the opening 20 seconds of the fight - but, from that moment, Collazo's clean counter-punching caused no end of problems.
And afterwards Hatton, badly bruised around both eyes, conceded his ambitious move up to the 147lbs weight limit for the first time had proved more difficult than he had initially envisaged.
Hatton said: "I still believe I am a light-welterweight but, moving up a division, I did notice the difference and Luis hurt me several times in the fight.
"I am obviously giving guys a better chance because they are bigger than me but the way I was hit and hurt in the last round and my response to it showed I can cope."
Collazo predictably called for a rematch but, tellingly, added he believed Hatton would put his 41-fight unbeaten professional record in grave danger by continuing to pursue titles at 147lbs.
"He has got to move back down because I am not a puncher and I had him hurt. That shows you how much he needs to stay at 140lbs - but if he wants, he can prove it in a rematch," said Collazo.
Whether Hatton's performance - full of all the usual intent, but badly lacking his trademark spark and movement - was entirely to do with Collazo's style or was a more weighty issue, only he can answer.
But certainly the ability of Collazo - who boasted only 12 stoppage wins in 27 fights - to sting his challenger at regular intervals sounded an ominous warning of problems ahead.
Ultimately, it was Hatton's drive and determination which got him through an assignment few expected to be much more than a relatively routine world title win.
Hatton added: "I have won my third world title and slowly I am realising all my dreams. I thrive on challenges and I don't want easy fights because I am aware of how much time I have got left."
By the time Hatton had his arm raised in victory, it seemed a long time since the flash first-round knockdown which looked likely to earn him another early night.
Hatton blazed out of his corner and caught his opponent with a superb left uppercut that dumped him heavily to the canvas, although Collazo later protested he had been hit on the break.
It took Collazo some time to recuperate and it was arguably that period in the early rounds which enabled Hatton to build up the lead required to take the title.
By the third, Collazo was nursing a bad cut on the top of his head, but was slowly gaining control, repelling Hatton's advances with sharp counter-punching moves.
Boxing behind a tight guard, Collazo was offering no way through and instead drilling home the cleaner shots like the eighth-round right which made Hatton nod in respect.
Unwilling to surrender his unbeaten record despite what was clearly an off-night by his usual awesome standards, Hatton responded with two heavy left hands in the ninth.
And the scene was set for a grandstand finish with neither fighter able to believe with any degree of certainty that it would be their hand which would be raised.
Collazo took the last round in big fashion, firing home a series of left-handers that had troubled Hatton tempo-rarily reeling and looking favourite for a rare taste of the canvas.
Relieved Hatton added: "Scoring a quick knockdown is probably the worst thing you can do because you get a bit of a rush to the head, you steam in and lose your way a little bit. I thought it was a fantastic fight. Maybe I will have to watch it again but I thought I just edged it by a couple of rounds."
As a two-weight world champion who has broken through into the American market, Hatton now finds himself with an abundance of options but first faces crucial questions over his future.
Dominance would await back down at the lighter weight and any attempt to establish himself as the No 1 at welterweight would, on this evidence, present a far more risky road ahead.
Collazo is unlikely to get his rematch but he insisted: "He should have had to do more to take my title. He fought dirty and he was holding all the time because he couldn't take my power."