Jesse Vargas defends his World Boxing Association 'regular' junior welterweight title on the Manny Pacquiao-Chris Algieri undercard in Macau on Saturday undaunted by an opponent who has a huge motivation.

Antonio Demarco was told last month that his 13-year-old sister had been struck down with cancer

Mexico's Antonio DeMarco (31-3-1, 23 KOs) received the devastating news that his 13-year-old sister had been struck down with cancer on his arrival at training camp in the Philippines last month.

"I fight for the life of my sister -- it’s for her that I’m going in the ring," DeMarco told reporters Thursday.

His sister Mariana was diagnosed with bone cancer in the shoulder and has already started chemotherapy. DeMarco was distraught at the news but vowed to win the title to show her that the odds can be overcome.

"She would see everything in life can be accomplished with hard work. I'm fighting for her dream to have a life"

Unbeaten Vargas said he was aware of DeMarco's sad news, but said it would not affect the outcome.

"We spoke yesterday," Vargas told reporters Thursday. "He told me about his sister's situation which is very sad news for us as well. I told him I hope a miracle would happen.

"But with this it doesn't matter him having extra motivation, I'm still going to put him down. Instead of him lasting six, seven rounds it might make him last another round or two."

Vargas has his own motivational weapon in his corner in the form of ring legend Roy Jones Jr, the multiple world champion who has been training the fighter in his gym in Las Vegas, and his making his debut as a cornerman.

";He's taking me to the next level," said Vargas. "You're going to see a different Jesse Vargas."

Jones, the only man in history to start as a light middleweight and win a heavyweight world title, said he was loving being a trainer and it was a natural extension of his own critical personality.

"I'm always thinking and correcting mistakes when I see people fight, it's just that I wasn't in the corner with them," he told AFP. "Now I'm in the corner with the guy."