Former Cowboys DE Marshawn Kneeland Diagnosed with CTE by Doctor Following His Death in 2025

The family of former Dallas Cowboys defensive end Marshawn Kneeland announced through the Concussion & CTE Foundation on Tuesday that researchers at the Boston University CTE Center diagnosed him with stage 1 chronic traumatic encephalopathy (CTE).

Kneeland died by suicide in November 2025 at the age of 24, and his family ordered a postmortem brain tissue analysis.

"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," Dr. Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System, said in the release. "Thanks to the generosity of our brain donor families, we now better understand the earliest stages of CTE, and it is bringing us closer than ever to diagnosing it during life. My team and I are fully dedicated to finding effective treatments and a cure for CTE."

The Cowboys selected Kneeland in the second round of the 2024 NFL draft following his five-year run at Western Michigan. He appeared in 18 combined games over the 2024 and 2025 NFL seasons and recorded 26 total tackles, a fumble recovery and a pass deflection.

"Mr. Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE," Dr. Chris Nowinski, Concussion and CTE Foundation CEO, said in the release. "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."

Kneeland's family is currently declining interviews and has asked for privacy as they continue to grieve.

"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," his family and his girlfriend, Catalina Mancera, said in a joint statement. "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."