"Maybe restarting training on the firmish grounds brings it on or maybe it is just an inherent problem.
"We are trying to sort it out now with injections. That is what we did last November and it worked. Hopefully these work and by the time we come back from South Africa he should be okay."
Ferguson expects Hargreaves to link up with the other senior stars who remained in Manchester and could yet be involved in a reserve team outing at Oxford on July 26.
Certainly the United camp remain confident Hargreaves will be fit when they begin the defence of their Premier League crown against Newcastle in five weeks.
"Owen is not written off for the start of the season at all," he said. "I am sure he will be okay."