Thomas was among Chiefs' final cuts

Former Dolphins great Zach Thomas has filed a grievance against the Kansas City Chiefs for his 2009 salary for cutting him without an injury settlement after he suffered a concussion early in training camp.

Thomas' grievance caps a week where results of an NFL-commissioned report concluded NFL players are more susceptible to dementia and the NFL Players Association formed its first committee to study concussions.

Thomas, a victim of multiple concussions in his career, visited the Pittsburgh Brain Imaging Research Center, sources said. Doctors told Thomas that his career was in his hands but the linebacker never played in a preseason game for the Chiefs. Thomas was among the team's final roster cuts.

Neither the concussion Thomas suffered nor his visit to the Pittsburgh research center were made public.

While, Thomas' agent, Drew Rosenhaus, claimed Thomas wanted to play again, sources said those prospects are slim.

A Chiefs source said Thomas was cleared to play by doctors and the decision to cut him was performance-based.

Chris Mortensen is ESPN's senior NFL analyst.