WBO world champion Joe Calzaghe admits he could retire early if Mikkel Kessler wins their super-middleweight unification bout on 3 November.
Joe Calzaghe may consider quitting if he loses his next fight
The unbeaten Welshman previously said his glittering 43-fight career is just "two or three" bouts from the end.
But an "unthinkable" result against unbeaten WBA and WBC champ Kessler could make him finish sooner.
"I don't know what I'd do if I lost," he said. "My unbeaten record would go and that's important to me."
Calzaghe sees his opponent as "potentially" his toughest yet, but said he is confident of winning.
"I never think about losing," he added. "If you're a boxer that kind of thinking is unhealthy.
Mikkel Kessler will bring the best out of me whatever way we go at it
"But yes, I know it's a possibility. Of course it is. You never know in this sport, he could catch me with a lucky punch or whatever, he's a great fighter.
"Anyway, as good as Kessler is I don't really see myself losing."
Calzaghe, 35, who is seven years the Dane's senior, is bidding to level Sven Ottke's divisional record of 21 title defences.
But he admits he is unsure what kind of fight will pan out in the Millennium Stadium, but is certain his performance will be better than those he produced in his last two outings.
He added: "I don't reckon it'll be a scrap, he's more your typical European stand-up fighter - great boxing skills, straight lines, good punch - but I'm prepared for anything.
"He will bring the best out of me whatever way we go at it. I always fight better against better fighters."