Sprawled out on the floor, he’s any ten-year-old in America watching Monday Night Football after his curfew. As the quarterback scores, he briefly sees himself on the TV screen, grinning, the roar of the crowd loud enough to make him forget his position in an otherwise quiet living room. He begs his parents to let him sign up for football. By the time he graduates from high school, he’s receiving offers from across the country; the end of college sees him signed on for a promising five-year contract with his dream team — the same one he watched growing up.

Ten years later, despite retiring from football, he struggles to adjust to life without the game. His wife has to repeat things she told him that morning. His friends note his increasingly frequent absences in their lives. The irritability he once channeled out on the field against opponents is now aimed at his children over a misplaced fork or a question asked twice. In many ways, he’s becoming a stranger to himself and the people around him.

With an average career length of six years, players in the NFL enter the league knowing the window is short — play hard, earn what you can, and move on to the next chapter. What neither they nor their fans anticipate is how long the game follows them into retirement. For some, no one will know the full extent of the damage until long after they’re gone.

In 2005, Dr. Bennet Omalu published the findings from an autopsy of the brain of former Pittsburgh Steelers center Mike Webster. Webster, who played in the league for 17 years and earned many accolades for his aggression and durability, struggled to adjust to life post-retirement. His increasingly erratic behavior (such as urinating in the oven, tasering himself into unconsciousness, and threats of killing strangers), sparked concern from his family. Following Webster’s death in 2002, Omalu examined slices of his brain under a microscope and was shocked to discover thousands of neurofibrillary tangles made up of tau protein — ordinarily responsible for transporting nutrients within brain cells — clustered throughout the tissue. Though tau tangles of this kind had traditionally been associated with Alzheimer’s disease, Omalu identified this as the product of a different affliction: Chronic Traumatic Encephalopathy, also known as CTE.

CTE , a progressive neurodegenerative disease caused by repetitive blows or trauma to the head, belongs to a wider class of brain diseases known as tauopathies . Repeated impacts cause tau to misfold and accumulate into tangles, which then damage and kill surrounding neurons. While it’s not uncommon to see athletes contract CTE from sports such as boxing, rugby, and ice hockey, the condition disproportionately affects American football players. A study published in 2026 estimated that at least 24.5% of former NFL players who died between 2016 and 2021 had CTE, a figure described as being on “the low end.”

Despite this and subsequent studies from other research groups, the NFL has been reluctant to acknowledge the outright connection between football and CTE. Traditionally, a definitive diagnosis of CTE was only possible through post-mortem examination. Thus, the league could attribute behavioral and cognitive decline in its players to other causes — aging and stress, or the general toll of a physical career. That, however, is beginning to change.

In 2026, a team in Toronto developed OXD-2314, a PET tracer capable of detecting CTE-associated tau in living retired athletes for the first time. In scans of these athletes with suspected CTE, the tracer detected tau deposits in brain regions consistent with the disease - results that were later confirmed through post-mortem examination. Similarly, another group of researchers at Washington University found that a blood protein marker originally developed for Alzheimer’s disease may also help track CTE severity in living people. Taken together, these developments represent the first steps toward identifying CTE in living patients, potentially giving players answers while they’re still around to hear them.