Johnson has been sidelined with tendinitis and a rotator cuff strain in his left shoulder and has not pitched in a game this spring. He met with Dr. Michael Milne on Monday.
"He is not ready to start a throwing program yet," said head athletic trainer Barry Weinberg. "We're going to give him one more week of treatment. At that point, Dr. [George] Paletta will examine him. We want to get him completely asymptomatic before he starts any throwing."
Cardinals officials acknowledged that the development is a concern, if not necessarily a major surprise. Johnson entered the spring projected as the top lefty specialist in the St. Louis bullpen.
"It's significant," said manager Tony La Russa. "We don't have an idea yet when he's actually going to be pitching. So, yeah, it's definitely a setback."
It was already expected that Johnson would not be ready by Opening Day, but this latest news cinches it. Once Johnson can begin throwing a baseball, he would still need a couple of weeks -- at bare minimum -- before he could appear in a Major League game. Instead, he will likely have to participate in some combination of extended Spring Training and Minor League rehabilitation outings.
"I have no idea what they're going to do with me," Johnson said. "It's up to them. All I'm going to do is make sure I'm 100 percent healthy, and when I am ready, I'm going to compete and hopefully try to make it back and help the team win."
Johnson was scratched from a scheduled appearance on March 1 after feeling tightness and weakness in his shoulder while he warmed up to pitch in a game. He has not thrown since.
"It is getting better," he said. "I think it's just a lot of inflammation in there, and having to get rid of it, it's not going to go away overnight. I'm real disappointed in the fact that I'm not going to get a chance to go out there and compete and try to earn a spot on the team. Because it's not going to happen."
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.