Detroit Lions veterans Grady Jackson and Bryant Johnson both started training camp today on an NFI list and general manager Martin Mayhew refused to reveal any details, other than to say he expects both players to be back "soon.'' Jackson, a 12-year veteran defensive tackle, was placed on the Non-Football Illness list with an undisclosed health problem. Bryant, a seven-year veteran receiver, was placed on the Non-Football Injury list with an undisclosed injury, not related to football.