The Nats' left fielder, who has spent the last couple weeks battling a lat strain, underwent an MRI to see if there was anything more which was causing him discomfort when he throws.
The test confirmed the lat strain and didn't reveal any further issues, but Morse will continue to be held out of the lineup for now. He'll be allowed to get some swings on a side field, but will not play in Grapefruit League games.
Same goes for first baseman Adam LaRoche, who still has some pain on the outside of his foot when he makes turns.
"They've still got some discomfort. Even though they've both been in there playing, they're not 100 percent," Johnson said. "My conversation with the trainer today was, '(Rick) Ankiel, LaRoche and Morse - treatment over here, they can hit over there, work out under your supervision, but I'm going to be on the cautious side.' We've got a ways to go. Those guys don't have to prove anything to me.
"My main concern is getting them ready. I don't want to have this conversation every day where I'm asking (the trainer), 'Are they ready?' or "How they feel?' or 'What's the doctor say?' I don't want to have that conversation every day."
Ankiel is still limited by a hamstring injury.
Morse, who was expected to be the starting left fielder and cleanup hitter for the Nationals this season, has yet to play the field because of the lat injury. All of his Grapefruit League action has been at DH. LaRoche, meanwhile, returned after missing the first part of camp due to shoulder and foot problems, and has played in four spring games. But the foot is still plaguing him.
So how long before fans should start getting worried? How much legitimate spring training action would Morse, LaRoche and Ankiel need to get themselves fully ready for opening day?
"Ideally, (with) 4-5 games to go, I like everybody timing everything, kind of feeling good," Johnson said. "And then I actually back off of them all and give them enough for maintenance and play the other guys.
"A lot of times, it's great to have (injuries) this time of year, when you're pushing your body. A lot of times, when the quality of talent is better in your camp, guys push themselves harder earlier, and you're more apt to have that kind of problem. But with roughly three weeks to go before the season, I'm happy it's now. Because you know you're going to have those kinds of things happen."