Johnson was scratched from Thursday's start due to shoulder fatigue, Alex Speier of The Boston Globe reports.
There was tons of speculation that the scratch was a response to the David Price (elbow) injury earlier in the day, but apparently there's also an injury in play for the minor-league hurler as well. However, those close to the situation don't expect Johnson to land on the minor-league disabled list due to this issue, so consider him day-to-day for now. If he does get back on the mound soon, though, there is a good chance he could head to Boston to provide a fresh arm at some point in August.