When Michael Katsidis climbs into the ring against Juan Manuel Marquez on Saturday in Las Vegas, little more than a month will have passed since the death of his brother.

Stathi Katsidis, a champion jockey in Australia, suffocated on Oct. 19 after a drinking session that proved more than his tiny body could handle. He was 31.

Michael, THE RING's No. 1-rated contender at lightweight, made the choice to continue training in Thailand and fight on. Not even his brother's funeral, a nine-hour flight away, could convince him to break camp.

“The fight will go on!” Katsidis said in a statement. “I will do this for Stathi, my family and myself. The moment I walked in for a grueling sparring session after hearing the news of his death earlier that day, my trainer Brendon Smith shook my hand and said to me 'you are about to take the bravest step of your life.' We nodded, smiled and went to work.”

The Australian brawler won't be the first to climb between the ring ropes with a heavy heart. Daniel Jacobs, James “Buster” Douglas and Bobby Chacon are among those who have fought shortly after the death of a loved one.

The grandmother who raised Jacobs died in July, less than a week before he was due to face Dmitry Pirog for a vacant middleweight strap. The Brooklyn prospect elected to go through with the bout, but was knocked out in the fifth round.

“I thought about pulling out,” Jacobs told RingTV.com, “but another part of me wanted to do it to honor her, honor her name. I didn't really know how much of an effect it would have.”

“Because I was doing it for her, I thought everything would be OK. But I guess it didn't turn out that way.”

Jacobs, who cried in the dressing room before the fight, felt as if his speed was gone once he got in the ring.

His advice for Katsidis: “Take your time and evaluate the situation and really think about what you're doing before you continue with this fight. Because if you feel like you can't do it for any second, pull out.”

Jacobs' personal loss may have led to his professional one, but 20 years ago in Tokyo, another fighter famously found inspiration in grief.

Douglas, a 42-1 underdog, knocked out undisputed heavyweight champion and seemingly unbeatable Mike Tyson only 23 days after the death of his mother.

While an undertrained Tyson looked past Douglas to Evander Holyfield, Douglas, channeling his grief, had had the training camp of his life.

Unlike so many Tyson opponents, Douglas walked to the ring unafraid and fought the perfect fight. In the eighth round, he rose off the canvas at the count of nine and knocked Tyson out just one round later.

After the shocking knockout, when Larry Merchant asked him how he did what nobody thought he could do, Douglas replied: “My Mother, My Mother. God Bless her heart!”

And then he wept.

Today, Douglas says his faith and the challenge of grief and hardship brought out the best in him.

“That was the climax of everything that was going on in my life that was not in my favor,” he told RingTV.com. “Her passing just made me see the light; that it was my time to shine through all that adversity.”

It was Douglas' unwavering focus, in contrast to Danny Jacobs' distraction, that allowed him to control and hurt Tyson.

“I didn't think about it,” Douglas said. “I just thought about the fight itself. I felt good, I felt ready. I made it there for her. I was ready to go.”

Other boxers have simply soldiered through their pain. Chacon, a featherweight and junior lightweight Hall of Fame from Los Angeles, fought and won the night after an unimaginable loss.

Chacon's wife, Valerie, had pleaded with him to quit boxing. He refused again and again. The night before he was due to face Salvador Ugalde in 1982 , she despaired and shot herself in the head with a rifle.

Chacon now lives in a nursing home, unable to give interviews. His promoter, Don Chargin, remembers the fight as one of the most dramatic in his long career.

“I was trying to call the fight off,” said the 82-year-old Hall of Fame promoter. “Naturally, I figured we'd have to, but he insisted that it go through. He cried all through the fight until he knocked the guy out. He was crying in the dressing room, he was crying during the referee’s instructions and he was crying while he was fighting. It was a very, very dramatic time.”

Dr Jay Granat, a psychotherapist who has worked with professional boxers, believes that athletes like Chacon and Douglas can compartmentalize and use their grief, while others simply can't.

“Clinically, we know that it can take some people two years to be right after a shocking loss,” he said. “Boxers are still human and they could need that. Despite what the public thinks, boxers tend to be bright and sensitive. They're not robots or animals.”

Douglas and Chacon's triumphs over adversity and grief are part of what make this sport special, but boxing culture can be tough.

Only in boxing could fans and forum warriors interpret a 23-year-old talking about the death of his grandmother a few days before his first loss as 'excuse making', as some have with Jacobs.

Rightly or wrongly, many boxing fans expect men who step into the ring to be the embodiment of the warrior mentality, even after they lose, as Katsidis has been and will be.

But instead of expecting them to be superhuman, perhaps we should simply marvel at the courage of the men who step into the ring with a heavy heart, come what may.

Alex McClintock is a sports writer who lives in Australia