Johnson believes Marrero is another month or two from playing in a Major League game. Marrero tore his left hamstring while playing for the Licey Tigers in the Dominican Winter League this past offseason.
Marrero, who is considered a backup first baseman, hurt the hamstring stretching for a thrown ball.
Johnson believes the shoulder problems were caused by the fact that he was overaggressive during his rehab.
"I think the shoulder stuff is coming from a lot of hitting, throwing and a little weight work," Johnson said. "I'm not as concerned about some of the medical reports on the shoulder."