Johnson has missed large parts of several games due to injuries to his head, shoulder, ribs and knee. This week it's a knee injury, which he suffered in the first half against Florida.
"He's hurting," Richt said. "He's a little bit in the tank about it, but he's got to count his blessings. When it's your last shot as a senior, it's hard to stomach not being out there with your team."
Johnson is fifth on the team with 29 tackles despite all the time he has missed. He is tied for the team lead in interceptions with one.
"He's still doing a great job of being a leader out there," sophomore cornerback Asher Allen said. "He'll definitely be in our ear still. He'll make sure Reshad (Jones) is ready, and he'll make sure the whole defense is ready."
Jones, a redshirt freshman, will start in Johnson's place. Jones has 19 tackles in the last three games and is second on the team with 43 tackles. Houston County graduate Quintin Banks also will get more playing time due to Johnson's injury, Richt said.