This article is part of The Athletic’s series marking UK Black History Month. To view the whole collection, click here.

Lassana Diarra was preparing for the 2010 World Cup in South Africa. 

The midfielder, who had spells with Chelsea, Arsenal, and Portsmouth in the Premier League, was coming off the back of a difficult first season with Real Madrid. That campaign, 2009-10, he had made 30 appearances in all competitions for Manuel Pellegrini’s side as they finished second in La Liga, three points behind Barcelona. They had also crashed out of the Champions League at the last-16 stage against Lyon.

Keen to put an underwhelming club campaign behind him, Diarra, aged 25, joined up with the France squad — which included Thierry Henry, Franck Ribery, Hugo Lloris, Nicolas Anelka, and Karim Benzema — in a pre-tournament training camp. Tignes was the destination, chosen for its high altitude that would mimic conditions in South Africa.

However, on May 22, 2010, his hopes of playing on the world stage were dashed.

“Further to his intestinal pain contracted on the glacier in Tignes, check-ups have detected evidence of an unpredictable illness which justifies rest for an indeterminate period,” a statement from the France Football Federation read.

Diarra’s diagnosis was later confirmed as sickle cell anaemia.

The National Heart, Lung, and Blood Institute (NHLBI) defines sickle cell disease — the most common being called sickle cell anaemia — as a group of inherited disorders that affect haemoglobin (the major protein that carries oxygen in red blood cells). In sickle cell disease, red blood cells are misshaped, typically crescent- or “sickle”-shaped due to a gene mutation that affects the haemoglobin molecule. When red blood cells sickle, they do not bend or move easily and can block blood flow to the rest of the body.

Symptoms include painful episodes called sickle cell crises, an increased risk of serious infections and anaemia — where red blood cells cannot carry enough oxygen around the body — which can cause tiredness and a shortness in breath.

According to Healthline, a provider of healthcare information in the U.S., Black people are at a much higher risk of being affected by sickle cell disease. Researchers believe the reason lies in how this condition has evolved over time to protect against malaria — most common in sub-Saharan Africa, where sickle cell is prevalent. Having the sickle cell trait helps to reduce the severity of malaria.

The sickle cell trait is found in one in four west Africans and one in 10 Afro-Caribbeans. It is also found in people who originate from the Mediterranean, Asia, and the Middle East. It is less common in white Europeans.

Sickle cell disease and the sickle cell trait differ, as people with the trait carry only one copy of the altered haemoglobin gene and rarely have any clinical symptoms related to the disease, while people with the disease carry two copies.

The American Society of Hemotology say more than 100 million people worldwide have the sickle cell trait.

Despite how common the condition is and its sometimes fatal consequences, sickle cell is still a relatively unknown condition and its effect on sporting performance is lesser known still. 

Part of the conclusion of ‘A Case Study of Two Premiership Footballers with Sickle Cell Trait’, a 2014 study conducted by the British Journal of Sports Medicine (BJSM), stated that “further research would be necessary with a larger cohort in order to further establish the relationship between redox homeostasis (defined as the maintenance of a balance between reducing and oxidizing reactions within a cell) and sickle cell trait in athletes”.

The BJSM did not respond to requests for comment from The Athletic.

Geno Atkins, a former defensive tackle for the NFL’s Cincinnati Bengals, spoke on his experience with the trait earlier this year. “I knew from my research that it would not be good for me to play in high altitude, so I prayed I wouldn’t get drafted by Denver, which is at a high altitude,” he told the Centers for Disease Control and Prevention (CDC). “I ended up in Cincinnati and have played at a very high level without any adverse effects of the sickle cell trait.”

He added: “Having the sickle cell trait does not exclude an athlete from participating in sports; however, the training staff and coaches need to take precautions to ensure the athlete is not put in dangerous situations.” In this case, Atkins cited an example of training in extreme heat.

Former Bengals defensive tackle Geno Atkins (Ian Johnson/Icon Sportswire via Getty Images)

Professional basketball player Billy Garrett Jr and former NFL running back Tiki Barber are two high-profile sportsmen with the disease, and wide receiver John Brown, most recently of the Buffalo Bills, possesses the trait.

Dr Mark Gillett, a consultant in sports and exercise medicine, tells The Athletic: “I’m not aware of it (sickle cell disease) in Premier League football or high-level football. I’ve not really seen it an awful lot at all. I am surprised that I haven’t. I would think that a player with full-blown sickle cell disease would find it difficult to compete at that level, just because of the physical demands of the game.

“At the same time, if you have sickle cell trait, you have that type of disease whereby extreme physical stress, altitude, or hydration can produce some symptoms. We may be seeing players with that and just not recognising it.

“Most Premier League football clubs are very diligent in the way they screen players. I think players at risk would have had their profiles done. If they have sickle cell trait, doctors would know about it. At the grassroots level, I suspect it happens a lot.”

Altitude was cited by Raymond Domenech, France’s national team manager at the time, when speaking about Diarra’s World Cup withdrawal in 2010.

“He wasn’t ready physically, he was really exhausted,” he said. “The illness was triggered by the altitude. He had predispositions that we couldn’t detect in advance. He needs a good 15 days of rest to fully recover, and he will recover, that’s for sure. It won’t have any bearing on the rest of his career but he’s not fit to play in a World Cup.” Diarra did not respond for comment when contacted by The Athletic.

Diarra, left, speaks with Domenech during France’s pre-2010 World Cup training camp (Franck Fife/AFP via Getty Images)

When asked how top-level teams would react to a player with the disease, Gillett says: “If they did find that when screening a player, obviously they would have to group that with the other things we look for when we assess players. We would have to speak to the player about it and make sure that their treatment is optimised.

“It would be a concern for players and clubs. Particularly when you get to the end of the season when the weather gets hotter and you’re more likely to be dehydrated. Sometimes, games have more riding on them and become more meaningful. It is certainly an added stress for them. It is hard enough being a Premier League footballer without having that to deal with as well. It would be a significant worry for them.”

The extent of Diarra’s illness was later confirmed by his club at the time, Real Madrid. In a statement, they said that Diarra was “now resting at home following medical advice due to asthenic syndrome secondary to a sickle cell anaemia that will be subjected to a hematological study (the study of blood and blood disorders) in Lyon Hospital”.

Valerie Davis, a haemoglobinopathy nurse counsellor at the Sickle Cell and Thalassemia support project in Wolverhampton, wants footballing authorities to increase their efforts in raising awareness and educate people within the game about the disease.

“There needs to be sessions whereby everybody is encouraged to be screened, irrespective of ethnicity,” she says. “Often it is thought that only specific ethnicities, such as those from African and Caribbean backgrounds can be impacted by this disease. The truth is anybody and everybody can be affected. Anyone who has haemoglobin and red blood cells can be impacted by sickle cell. It is the least likely for someone who is not from those backgrounds, but it can impact everybody.

“It could be a start to encourage everybody entering the sport to be screened. They then could do more work to bring in an expert to talk about the disease. Over the years, there has been a stigma around the disease and there shouldn’t be at all. This could help highlight the importance of screening. If someone is a carrier, they are normally absolutely fine. With rest, hydration, and nutrition, somebody can live an absolutely normal life. 

“With a good lifestyle, it is a possibility that someone who is a carrier should have no issues going far in football. Even if they’re affected by the full-blown condition. I would encourage the football authorities to never reject someone based on them being a carrier of the sickle cell gene, but even with the full-blown condition with conditioning and support, it will not stop them from reaching the top.”

In 2022, former England international Emile Heskey discovered that two of his children had the sickle cell gene. He began giving blood and encouraging other Black donors to not only register but also be tested for the condition.

Emile Heskey revealed that two of his children have sickle cell trait (Mike Egerton/PA Images via Getty Images)

“We need a whole new generation of blood donors, especially people of Black heritage,” he told the Mirror. “Because they are more likely to donate better-matched blood to treat people with sickle cell disorder.

“Some patients with sickle cell rely on regular transfusions to stay alive. Giving blood is simple, easy and can save up to three lives.”

Davis shares Heskey’s sentiment in encouraging people to be tested for the disease.

“A lot of people do not know that they carry the sickle cell gene, perhaps until later,” she says. “A woman, for example, may only discover during pregnancy that she is a carrier of the gene.

“We are going all-out to educate people individually because sometimes people may know within their families that there may be a carrier but they often will deny they have it themselves. There is a stigma about the condition, so some people do not go and get screened for it.

“Unfortunately, partners decline screening and that is the sad case (that) very often we see the birth of children that are affected by sickle cell. There needs to be a lot more initiatives to highlight the importance of it. We need to explain ultimately what can happen if it is ignored.”

A treatment for sickle cell cure was approved by the Food and Drug Administration (FDA) in December 2023, with the therapy, called Casgevy, from Vertex Pharmaceuticals and CRISPR Therapeutics, becoming the first medicine to be approved in the United States. The same treatment was approved in the United Kingdom in November 2023, with experts calling it “a historic moment for the sickle cell community”.

However, in May 2024, the gene-editing sickle cell drug was not approved for National Health Service (NHS) use. The National Institute of Health and Care Excellence (NICE) did not recommend the gene therapy treatment, saying that it required “additional data” beyond the current proposal.

In September 2024, Pfizer voluntarily withdrew large amounts of the sickle cell disease treatment medication Voxelotor, sold under the brand name Oxbryta, from worldwide markets.

However, with stories like that of Diarra’s still sporadic within football, Davis believes the condition’s unpredictability means that conversations about sickle cell within the sport must continue.

“Like many conditions, there are varying degrees of the impact that it has on individuals but ultimately, it does limit because of the unpredictable nature of the condition, what very often people can do and when they can do it,” she says.

“Particularly in sport, and football, there is a lot of training and of course, a lot of commitment required to the sport. Somebody who is impacted or affected by sickle cell cannot always commit because they simply do not know when they will be affected. It is very hard to commit to a sport, especially football.”

Although progress has been made in the fight to find a cure to find a cure for the disease and raise awareness of the condition within sport, more needs to be done.

(Top photo: Franck Fife/AFP via Getty Images; design: Dan Goldfarb)