Kerby Joseph, Cam Sutton and Tracy Walker were staying loose, jogging gassers the width of the field during a special teams period at Detroit Lions training camp Saturday when their teammate, C.J. Gardner-Johnson, joined in.

Gardner-Johnson ran to meet the trio of defensive backs, reached down to touch the sideline, made sure his teammates did the same, then took off back the other way with a smile on his face.

The emotional leader of the Lions defense was back practicing on a limited basis five days after suffering what, for a brief moment, appeared to be a serious knee injury, and his presence was hard to miss.

"I’m contagious. I’m like the flu," Gardner-Johnson told reporters after practice. "I’m like the flu. It’s going to go through your body. It’s either you get it or you don’t get it, and that’s not because I’m cocky, it’s not because − no, it’s because I’m confident in my job, I’m confident with my coaches and my teammates and my trainers and my strength staff are doing for me and teaching me, so I think that’s why."

Gardner-Johnson refused Saturday to talk about the injury scare he suffered Monday, on the second day of camp, when he crumbled to the ground during a team drill clutching at his right knee.

Gardner-Johnson repeatedly hit the outside of his knee as trainers tended to him on the field and could not put pressure on his leg after they helped him to his feet. He was carted off the field and underwent an MRI that showed no structural damage.

Asked Saturday how scary the injury was and how relieved he was to avoid serious harm, Gardner-Johnson paused for 3 seconds and said, "No comment. Next."

Asked about the injury a second time, he said, "I ain’t talking about that. Next topic."

“Next comment. I’m good," he said. "God."

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Gardner-Johnson spent Tuesday, Wednesday and Friday working as part of the Lions' rehab group with Marvin Jones and Jameson Williams. He moved gingerly during workouts the first two days, progressed to light running Friday and took part only in individual drills and the Lions' walk-through and installation periods Saturday.

He praised Williams, who remained out of practice Saturday with a hamstring injury, in his media session as "one of the best receivers in the game right now."

"I ain’t going to lie, I’m ready for him to play," Gardner-Johnson said. "I don’t know about y’all, but he’s one of the best receivers in the game right now. You got to give him his flowers, and if you don’t, we’ll see when he gets off what he got — God forbid what happens but that’s his situation, not talking about it. But working out with him every day, Jamo’s ready. Don’t worry about it. He ready."

And he insisted, "I never missed practice," because he was on the field with teammates every day.

"I’m mentally in practice," Gardner-Johnson said. "I don’t think you understand what type of guy you got here. I ain’t miss nothing. I didn’t miss a practice, I didn’t miss a rep, I’m still out there. My teammates still see me. One thing people got to understand, this game of football, sometimes it ain’t about being the best physically, as long as you got to be the best mentally. So as long as my teammates know I’m out there helping them, coaching them, I don’t really care about what you say about 'be back at practice.' I’m always at practice."

Whether Gardner-Johnson's presence made a difference or not, the defense had its best day of camp Saturday.

Rookie cornerback Steven Gilmore forced a fumble and intercepted a pass while playing with the second-team defense, the Lions struggled to move the ball offensively during a physical run period and the defense kept the offense out of the end zone in a situational period at the end of practice, when Julian Okwara and Charles Harris had possible sacks and Jared Goff completed three of seven pass attempts.

Lions coach Dan Campbell said it was important to get Gardner-Johnson back this early in camp because the team's new-look secondary is still developing chemistry.

One of the Lions' top free agent additions of the offseason, along with cornerbacks Sutton and Emmanuel Moseley, Gardner-Johnson is expected to start at slot corner this fall, though he said Saturday that is not a given, and he told teammates as much during his absence.

"They (were) awesome," he said. "I told them, don’t hang their head. I’m still in the building. I’m in here at 6 o’clock every day, I’m going to beat you in the building regardless if I’m hurt or I’m not hurt, and I think that’s the level and the standard that I was raised up in with Dan and A.G. (defensive coordinator Aaron Glenn) before they got here. So I think that stuff needs to stay there, no matter where we at. So they took it as somebody needs to step up and the whole team stepped up and that’s how I feel, that’s why we’re turning up."

Contact Dave Birkett at [email protected]. Follow him on Twitter @davebirkett.