The midfielder made only one substitute appearance in the last campaign after missing 18 months of action through injury.

He did not have enough time to make England’s World Cup squad but it was hoped he could join United on their summer tour.

They leave for their training camp in Chicago on Monday but instead Hargreaves is having further treatment.

It is a massive blow for the player especially as United’s first match is in Canada, where he was born and raised, against Celtic in Toronto a week tonight.

Manager Alex Ferguson told MUTV: “The bad news is that Owen Hargreaves is back in America seeing a specialist.

“He will not be ready for the start of the season. I do not know when he will be back.”

Former United striker Andy Ritchie added: “It is just one thing after another. You have got to fear for the boy’s future. Let us hope it is not as bad as we all fear.”

Ferguson also fears Rio Ferdinand will not be ready for the first game of the season against Newcastle.

The England defender suffered a knee injury in training ahead of the World Cup match with the United States and was unable to play in South Africa.

Ferguson said: “Rio will probably not make the start of the season. It will be close. It depends on his progress over the next few weeks.”

While Ferguson is pleased with Michael Owen’s progress following a hamstring injury the striker will skip the tour as he builds up his fitness.

Ferguson said: “Michael is doing great. He is working in the gym every day. I do not think he will be fit to go to America but he should be ready for the start of the season.”

Antonio Valencia and Nani are expected to available for the Newcastle match, according to the Old Trafford boss, after suffering an ankle injury and broken collarbone respectively.

Meanwhile Anderson is on course to return in September following a knee injury.

Ferguson added: “Cruciates are cruciates. He is doing fine and working hard.”