Kell Brook has revealed his regret at remaining at welterweight for too long but insists it will not stop him returning to his peak at 154lbs.
The 31-year-old on Saturday at the Sheffield Arena begins his permanent move to the light-middleweight division, where he will fight Belarus' Sergey Rabchenko, best known for ending the career of Brook's one-time stablemate Ryan Rhodes.
He does so after two consecutive stoppage defeats, the first at middleweight by Gennady Golovkin when he fractured his right eye socket, and the second back at welterweight, where he surrendered his IBF title to America's Errol Spence and fractured his left.
The return to 147lbs from 160lbs contributed to his struggles against Spence after a career in which he has consistently struggled to make the former limit and long appeared a natural light-middle, but his desire to retain his world title drove him to do so.
"I regret the Spence fight," said Brook. "It was in Sheffield, we'd sold a load of tickets and we were in a football stadium (Bramall Lane).
"But going from middleweight down to welterweight was too much and it drained me; I was a proud champion and I never duck anyone.
"That really hurt me badly: it took me a long time to get over that. I've got a lot left in me: people are right to question what I've got left and how I am going to be after the injuries and the defeats, but I believe I'm going to be better with the bigger weight which will bring the best out of me.
"The eye has healed very well. It's held up in sparring and I don't think about the eye injuries at all. I wouldn't be boxing if I wasn't given the all clear by the doctors; I wouldn't put my family or myself through that."
Of the 32-year-old Rabchenko, who was once trained by Ricky Hatton and in addition to Rhodes has victories over Britain's Bradley Pryce, Kevin McCauley and Martin Concepcion, he added: "I didn't want an easy fight back. If I had done, I could've fallen out of love with it, cut corners and not reached the heights in training that I need to reach.
"Rabchenko is a dangerous guy; he's no mug and he can really bang. I've sparred with him and if you were to go on the sparring, it's going to be a hell of a fight."