Former Oklahoma DT Charles Walker was diagnosed with depression shortly after declaring for the NFL Draft during the 2016 season, according to NFL.com's Ian Rapoport.
Walker played in just four games for the Sooners as a junior before sustaining a concussion against TCU. After not returning to the field because of residual symptoms, Walker announced in November he would voluntarily sit out the remainder of the season and prepare for this year's draft.
However, after his declaration, Walker was diagnosed with depression, which could have been the cause of some of his concussion-related symptoms, according to letters sent to NFL teams by Walker and his doctor, Ashley Benjamin, MD.