Assistant general manager Thad Levine said Monday that the report was about as good as the team could have gotten.
Harrison was scratched from two throwing sessions last week after experiencing stiffness in his neck and back. He then returned to Texas to visit the doctor who last year did two operations for a herniated disk in his lower back.
The plan is for Harrison to resume cardio and conditioning Wednesday, and play catch the following day.
Levine says it's not clear how far behind Harrison is, but acknowledged it's unlikely he'll be ready for the start of the regular season in five weeks.