London - Aries Merritt thought he had run his last race two years ago as he underwent a kidney transplant, but against the odds he is a contender to add the 110m hurdles world title to his 2012 Olympic gold.
The 32-year-old American - who enjoyed an annus mirabilis in 2012 by taking gold in London and then breaking the world record with a time of 12.80 seconds - has shown some smart form this campaign.
He returned to winning ways, including in the London Diamond League meet on the same track where he won the Olympic title and where he will bid to win the world crown.
Victory in London might even outdo Merritt's bronze in the 2015 world final in Beijing when he was just days away from the transplant - the kidney donated by his older sister LaToya Hubbard.
"A lot of it was because I thought it was probably going to be my last time running ever again," Merritt told the New York Times last year, referring to the effort he put into winning bronze in Beijing.
"And so I just pulled a rabbit out of a hat, essentially."
The slightly-built Merritt's performance in China even had Leslie Thomas, his kidney specialist at the famed Mayo Clinic, in awe of the achievement.
"He had almost no kidney function, terribly anaemic, running against the Chinese fog or smog, and he came in third!," Thomas told Sports Illustrated in 2016.
"Don't you think that's amazing? I mean, that's, like, crazy."
LaToya said she didn't think twice about donating her kidney to Merritt, whose illness was a a rare congenital kidney disease called collapsing focal segmental glomerulosclerosis (FSGS), first diagnosed in 2013.
Indeed back then she was pregnant, with her daughter Lela, but contemplated terminating her pregnancy so as to donate her kidney - however that radical step was avoided as Merritt's condition improved enough to delay the procedure.
"I'm not going to say I was disappointed," Hubbard told the New York Times last year.
"It was more like, wow, what can I do to help my brother? I just decided to do what I could do."
Merritt, who despite a lack of race fitness only narrowly missed out on a place in last year's Olympic team, says LaToya has always been there for him even if in the early days it was tough love.
"She was really tough on me as a kid, growing up as an African-American in Atlanta, in the ghetto; well, not in the ghetto, but not in a rich area," he told Sports Illustrated.
"It was tough and she made me see things I wouldn't normally see. She toughened me up for the harsh reality of the world in the USA. I love my sister to death."
Their mother, though, intervened to get LaToya to ease up on her brother.
"When I'm gone, it'll only be you two," she told the Washington Post.
"You have to look out for each other."
LaToya took the message to heart and Merritt, who had to undergo further surgery later in 2015 to have the kidney pushed deeper inside his body, could reward her extraordinary gesture with gold in London.
Indeed Merritt's mindset has completely changed from two years ago when he contemplated life without athletics.
"I was told, 'you'll never come back to the sport with the medications you have to take that are life long'," said Merritt, who will take three different medicines daily for the rest of his life.
"It was something that went in one ear and out the other.
"No matter what someone may tell you, whether it's a doctor or not, you can't give up hope. You always have to stay positive and look at the brighter picture."