Johnson (concussion) is not participating in Thursday's practice, Matt McMullen of the Chiefs' official site reports.
Johnson, who was placed in the concussion protocol during Kansas City's win over the Raiders in Week 8, will need to gain full clearance in order to be eligible for Monday's contest against the Buccaneers. In order to foster optimism about his chances of playing Week 9, Johnson will likely have to upgrade to non-contact practice activity by Friday.