“It ain't over 'til God says it's over. Man can't tell you it's over - if that was the case a lot of people would have written me off three years ago.” Roy Jones Jr was back on the defensive again. Once regarded as among the greatest boxers of all time, now he has to prove that he is not just another legend chasing a last big cheque.

He keeps telling people that he is as good as ever; fewer of them believe him. All great fighters fade away and few go quietly. Joe Calzaghe remains insistent that Saturday's bout with Jones at Madison Square Garden will be his last, but he is the exception.

Jones, 39, has been far less attentive to the effect that time has had on his skills. There is little doubt that he is a modern-day great. He rose to prominence after a controversial defeat by a Korean in the light-middleweight final at the Seoul Olympics in 1988, but the incident gave his professional career a kick-start. Within five years, he beat Bernard Hopkins for the IBF middleweight title. A year later he took James Toney's WBC super-middleweight title and beat Mike McCallum to become world champion at light-heavyweight - a title that he would hold for nearly eight years.

He bulked up to make history, winning the WBA heavyweight title from John Ruiz in 2003, around the time that he took a role in the film Matrix Reloaded. He also started a career as a rap artist and was talking about trying out for the NBA. Then the slide started and the star faded.

Three successive defeats, against Antonio Tarver (twice) and Glen Johnson, the latter an ugly knockout, seemed to spell the end. He was written off by many, including, in his autobiography, Calzaghe. But three comeback wins, one of which was over Félix Trinidad in January, put Jones back in the picture.

“I'm feeling better than ever, the training camp was wonderful, I'm having the time of my life,” he said. “When you get a fighter as good as Joe come out and say 'I want to fight you', that means a lot. This is what I do for a living, this is what I love. They thought I was gone - wrong.”

Jones, though, remains a strong underdog. A full beard, which he will have to shave off before the bout, helps to give him the appearance of an older man and against Calzaghe, 36, who probably throws more punches than any boxer at such a high weight division in history, he must avoid being overwhelmed.

“More of the pressure is on Joe,” Jones said. “He's going to start throwing punches tomorrow and through the weekend. People say he throws pitty-pat stuff, but he can punch. I could never match the output that Joe will throw. But what you have to think about is if Joe will be able to match me. In pro boxing, you always have to worry about one big punch.”

Jones does give one concession to his advancing years. “Now I cannot play a full basketball game and fight the same day,” he said.