ALLEN PARK, Mich. -- The Detroit Lions are fairly healthy going into the start of training camp, except at one spot: head coach.

Second-year Lions coach Matt Patricia wheeled into his first news conference of training camp Thursday morning on a cart. He had surgery on his left leg earlier this summer.

"It's nothing, just something that with the tendon back there and the bone and the muscle, again, I don't have a lot of time to fix that stuff," Patricia said. "So doctors went in, cleaned ... some stuff up in there.

"We all need training camp."

Patricia called himself day-to-day. He said the injury will take him 10 to 15 yards away from where he usually likes to be in the middle of practices trying to teach players. He is typically a hands-on coach who will jump in with different position groups to help instruct throughout practices.

While injured, he won't be able to do that.

"It's something that I'm really trying to be careful with it so I don't have any setbacks from that standpoint," Patricia said. "So probably maybe a little bit overcautious, when I can be. ... It's a long season."

As far as his players, the Lions placed Damon Harrison, Darius Slay and Darius Kilgo on the non-football injury list. Harrison and Slay both missed all of spring workouts, and the moves are precautionary to get them up to speed.