Johnson described his condition as "a little strain" and playfully chided reporters for rushing to his locker for an update.
"I had a little problem in the offseason and went and saw a doctor and we've been working on it," he said. "Everything's fine. I'll just be a week behind schedule. It's taken care of.
"It's just a back problem. There was no incident. I went and saw a doctor. It's no big deal."
Asked if he still feels any discomfort when he wakes up in the morning, Johnson replied, "No, no, no. Everything's good."
Johnson is doing stretching exercises for his back, which flared up at the beginning of January. He won't do as much running in camp, "but we've got all these new toys here in the training room," he said.
Johnson will play catch today as part of the Orioles' first workout for pitchers and catchers.
"I'll be on the mound fairly soon," he said.
Meanwhile, Johnson still doesn't know whether he'll set up or close this season.
"That's what spring is for," he said.
The only certainty is he won't be a starter.
"With the way things happened with the back, that pretty much put the nail in the coffin on that because the conditioning kind of got hit with that," he said.