Former Cowboys DE Marshawn Kneeland diagnosed by researchers with stage 1 CTE
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Researchers at the Boston University CTE Center have diagnosed Marshawn Kneeland with stage 1 (of 4) chronic traumatic encephalopathy (CTE), the family of the former Dallas Cowboys defensive end announced on Tuesday through the Concussion & CTE Foundation.
The 24-year-old Kneeland died by suicide in November from an apparent self-inflicted gunshot wound.
"Unfortunately, I was not surprised to find CTE in the brain of Mr. Kneeland, because we have found this progressive brain disease in nearly half of the athletes we've studied who have died before the age of 30," said Dr. Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System.
"Mr. Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE," said Dr. Chris Nowinski, Concussion & CTE Foundation CEO. "We have no reason to believe the current generation is at a lower risk of CTE than previous generations. Concussion protocols do not prevent CTE, because CTE is caused by repeated head impacts, not just concussions. If we want to reduce CTE risk, we must implement CTE prevention protocols and aggressively reduce the number and strength of head impacts at every level of the game."
Stage 1 is the earliest stage on the scale of 1-4.
According to the CTE Society, stage 1 can be marked by "short-term memory problems, depression, aggressive tendencies, explosivity, and executive function issues."
Kneeland was the Cowboys' second-round pick in the 2024 NFL Draft and played 18 games with the team. As police searched for him, his girlfriend, Catalina Mancera, reportedly told them he had a history of mental health issues.
"While this diagnosis does not change the tragedy of his passing, it provides important context about some of the struggles he may have been facing," read a statement from the Kneeland's family. "We share this information to help people understand what NFL and other high contact sport athletes might be struggling with. Raising awareness is important to us. We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life. One Love."
The Cowboys honored Kneeland for the remainder of the 2025 season by wearing No. 94 decals on back of their helmets and special blue Kneeland T-shorts with his face on them during pregame warmups. After their win over the Las Vegas Raiders, defensive lineman Osa Odighizuwa found Kneeland's jersey and carried it off the field with him to the locker room.
Last month, Mancera announced that she had given birth to the couple's baby boy on June 11.
