Danny Williams has admitted defeat to Scott Gammer in Friday's British Heavyweight Championship in Neath will spell the end of his boxing career.
Williams is in "very good shape" ahead of his fight with Gammer
The 33-year-old faces Gammer, unbeaten in 18 fights, in an attempt to get his career on track after defeats to Audley Harrison and Matt Skelton last year.
And he conceded: "If I lose this fight, I am finished. This is my last chance.
"People have written me off, but Gammer and his camp have underestimated me. I have a lot to prove and I'm motivated."
Title-holder Gammer, 30, is desperate for victory as he looks to prove himself Britain's best heavyweight ahead of a possible world title bout.
But Williams is in confident mood, saying: "I've done a lot of sprints, road work and sparring and feel really good. I'm in very good shape.
"For the last few fights I haven't been in good shape or prepared properly.
After I beat Gammer I will be looking for revenge with Skelton and maybe Harrison. Those defeats hurt big time
"Gammer is young, strong, has a good offensive game and a fair dig on him. He's a good fighter but I've shown my heart, determination and punching power.
"This isn't the first time people have written me off and I've always come back."
And Williams is already considering a rematch against Skelton or Harrison should he dispose of Gammer.
"After I beat Gammer I will be looking for revenge with Skelton and maybe Harrison," he said.
"Those defeats hurt big time, not only because I lost but because I wasn't performing. It hurt a lot but I always transfer the negatives into a positive."