Kuala Lumpur - If Manny Pacquiao wants to know all about comebacks, he need look no further than his conditioning coach Justin Fortune.
The former heavyweight, who in 1995 went up against the great Lennox Lewis, found himself in an altogether different fight when a dental check-up four years ago discovered he had throat cancer.
"What do you do? You either roll over and die or you fight," Fortune told AFP in Kuala Lumpur, as the 52-year-old put the finishing touches on Pacquiao's return to the ring against WBA welterweight champion Lucas Matthysse of Argentina at the Axiata Arena on Sunday.
"They're your only two options. There is really no other choice," said the Australian, who had chemotherapy, radiation therapy and surgery, and is now in remission.
"My salivary glands are almost all gone," said Fortune. "I was lucky to keep one, and I've got 90 percent of my tastebuds back.
"It's hellish: chemo, seven weeks of radiation and they chop you up as well. But they can't kill me yet."
Pacquiao, 39, will be back in the ring on Sunday for the first time since losing his World Boxing Organisation belt in a shock decision to Australian Jeff Horn on July 2 last year, after which he resisted calls to quit.
And Fortune, who has been in the Filipino former eight-weight world champion's corner since 2002, said the world would see "the old Pacquiao" thanks to a shake-up in his training regime.
"Manny's 40 this year and you know we changed things up this time," said Fortune. "We did a whole bunch of different work. We were shocking his system back into working.
"He's been doing the same stuff for 16 years so he probably gets so used to it.
"But now it's a different style of training - shorter, faster and more intense. So his body reacts differently. So that's why he looks like the old Pacquiao."
That could be bad news for 35-year-old Matthysse, who has knocked out 36 of his 39 victims, while Pacquiao's last stoppage victory was against Miguel Cotto way back in 2009.
"He overtrained for Jeff Horn, for sure, 100 percent," said Fortune of Pacquiao's flat performance a year ago which saw him lose a controversial unanimous decision.
"He's just stubborn sometimes. He learnt his lesson. All I had to do was sit down and say to him: remember last year," said Fortune.
"We don't want to overtrain. This guy Matthysse is a lot better than Jeff Horn, he punches a lot harder. He's a better fighter. He's much more dangerous."
Fortune said Pacquiao would have no trouble making the 147-pound (67kg) limit for his World Boxing Association welterweight challenge to Matthysse at Saturday's weigh-in.
"He's the only fighter I know that has to eat to make weight," said Fortune, who added that the Filipino could easily drop down two divisions to lightweight if he wanted to, even in his 40th year.
"He could make 135 pounds inside of four weeks. His metabolism is ridiculous. I don't know what it is. He's a freak."