Sir Alex Ferguson has revealed that Michael Carrick is set to miss three weeks with an Achilles injury.
The problem means the Manchester United midfielder will be sidelined for a crucial run of fixtures, at home and abroad.
The Red Devils travel to Everton on Saturday, for a fixture which can be seen live on Sky Sports 2, HD 2 and in Sky 3D, while they are due to get their UEFA Champions League campaign up and running with a Battle of Britain clash with Rangers on Tuesday.
Ferguson's men then return to domestic duty on 19th September with a mouth-watering meeting with old adversaries Liverpool at Old Trafford.
England international Carrick will sit out each of those fixtures, and could also miss away dates at Bolton and Valencia as United look to make inroads in the Premier League and in Europe.
The 29-year-old has found himself on the fringes of the first-team so far this season, making just one substitute appearance, but he remains an important squad player for Ferguson.
The Scot revealed on Thursday that Carrick has already visited a specialist in an effort to determine the severity of his injury, but admits that he will be out of action for the foreseeable future.
"We've had a little setback with Michael Carrick," said Ferguson.
"He's out for three weeks with an Achilles problem, maybe a month at most.
"It has been bothering him for a few weeks now, so we sent him to a specialist in London yesterday and he had an injection.
"We are hoping that settles it down. We have been considering what we should do about it. The best thing is to get it treated and out of the road now."
Ferguson also revealed that Brazilian midfielder Anderson picked up a slight knock during a reserve run-out against Stockport on Thursday.
"Anderson came off with a niggle last night but it won't knock him back for long," he added.
While his midfield options have been depleted ahead of a weekend trip to Goodison Park, Ferguson is set to welcome Rio Ferdinand back into the fold on Merseyside.
"Everyone else is fit," he said.
"Rio's in the squad - he wanted to play last night but his training performances are so good, he doesn't need to."