"I doubt we'll get Rooney fit for the start of the season with the virus he's had," United's boss Alex Ferguson told Skysports.com

"He picked it up in Nigeria and it's not a nice one. It's 12 days to the season starts and he's not been able to train."

The England Champions had a pre-season in Nigeria and won the Vodacom Cup last month.

The Scot will have to do without many of his key players as Cristiano Ronaldo is still out with an ankle injury, Portuguese winger Nani is banned from the league opener against Newcastle while Brazilian midfielder Anderson is on international duty at the Olympics in Beijing.

"I'm starting to worry about whether we are going to have a team ready for the start of the season," added Ferguson.

Manchester United didn't recruit any new players but the club admitted that they are at an advanced stage of talks with Tottenham striker Dimitar Berbatov.