JUPITER, Fla. -- Concern is growing that Michael Morse will not be ready when the Nationals begin the regular season on April 5.

The Nationals do not know when Morse, who has been out for most of the spring with a lat injury in his right shoulder, will be ready to return to action.

"I'm not discounting it and I'm not counting on it," manager Davey Johnson said of Morse's availability for Opening Day.

One thing that is certain is Morse will not be available soon. Johnson believes Morse recently received an injection of platelet-rich plasma to help his ailing lat muscle.

"With as big and strong as Mike Morse is, they did this new procedure -- the PRP or whatever -- where you put stuff in and it helps it heal," Johnson said. "That's what I just learned. It gets in there and helps the healing. That's a kind of new science as far as I know."

Platelet-rich plasma therapy is a treatment that involves putting the patient's blood through a centrifuge to isolate platelets and growth factors. Those are then injected back into the injured area to accelerate both healing and tissue growth.

Several prominent baseball players such as Yankees third baseman Alex Rodriguez and Orioles pitcher Zach Britton have recently used PRP to help in their recovery from injury.

"The diagnosis showed a little tear, a small tear," Johnson said. "It's an aggressive treatment to help it heal. You look at it a week after that treatment. I'm not sure when that treatment was given or when the diagnosis was given, but it's been three weeks since the injury. He's probably more of a candidate to not open the season."

Johnson admits the Nationals are being very cautious with Morse. They want the man who hit a career-high 31 home runs last year to be healthy when he returns to action.

But caution alone does not comfort Johnson as he prepares to manage the Nationals this season. He would like to have a better idea of when the powerful Morse will be available so he can plan for filling his spot in the interim.

"In my era, you'd take a couple of days off and go get 'em," Johnson said. "Now, we're more cautious and it's better for the player, not only in the immediate future, but long-term future. I still like to have a more definitive answer on guys so that I can make alternate plans."

Morse was supposed to be a big part of the Nationals' lineup this season. Johnson envisioned hitting the 30-year-old fourth behind star third baseman Ryan Zimmerman. But Johnson is already planning for a new cleanup hitter in case Morse is unavailable.

"[Wilson] Ramos and [Jayson] Werth," Johnson said of his options. "I really like Werth's approach this year. I like where he's at. I think he's priming for a big year. But it's early. We've got about 14 games left. Not knowing the time frame, I do like to have a left-handed presence in the lineup. So that works for [Chad] Tracy, and [Rick] Ankiel is back. We've got time to look at things."

Johnson also has a bevy of options to fill Morse's spot in left field. The Nationals currently have Jason Michaels, Brett Carroll, Roger Bernadina and Ankiel in camp competing for roster spots. They also have a pair of intriguing options that can play the outfield in a pinch in Mark DeRosa and Steve Lombardozzi.

"I think Mike Rizzo did an outstanding job with the winter he had," Johnson said. "He added a lot of good options. Everybody has to be able to sustain injuries. We're not the only ones who have to look at it."

Another option that could factor into the discussion in a few weeks is Xavier Nady. The veteran recently signed a Minor League deal with the Nationals and is working himself back into shape. If he impresses, he could join the conversation, because he has experience playing first base and left field.

Even though Washington has several fall-back plans in place, Johnson ideally wants Morse back healthy as soon as possible. But that does not mean the Nationals are going to push Morse into playing before his injured lat can handle it.

"We're doing everything we can on our end," Johnson said. "Our medical crew is second to none. We're going to be very cautious at this time of year. They're valuable assets, and we're going to take care of them."

Typically, a team would like to see a player perform in games before putting them in the big leagues. But that does not mean that Morse has to play in the Grapefruit League in order to earn a spot on the Opening Day roster.

"I had a conversation with him where I said, 'Do you think you can get enough at-bats on the Minor League side where you'd be comfortable over here?' Johnson said. "And he said, 'Yeah.'"

All the uncertainty surrounding Morse's injury has caused a lot of concern and confusion among the Nationals' staff. After meeting with the media for nearly 30 minutes on Thursday, Johnson summed up the situation with an interesting but slightly optimistic statement.

"Just to be clear, it's really unclear," Johnson said. "The fact that he feels fine and doesn't feel discomfort is good. I always like to know how the player feels. That's a good sign."