LONDON -- England striker Wayne Rooney faces an anxious wait to discover if he will be fit for the World Cup after suffering a foot injury in Manchester United's Premier League defeat at title-winners Chelsea on Saturday.
Rooney fell heavily under a challenge from Paulo Ferreira after 78 minutes and immediately held his right foot, grimacing with pain.
The striker, who will undergo a scan in Manchester on Sunday, was carried off on a stretcher and left Stamford Bridge on crutches.
United manager Alex Ferguson said he did not know the full extent of the injury but did confirm Rooney would not play on Monday against Middlesbrough.
"We don't know how bad it is yet," Ferguson told Sky Sports. "We will have to wait to get him back to Manchester. It's a sore one and we'll just have to wait and see.
"You always worry when one of your players takes a knock, but hopefully it's not a bad one."
Rooney is seen as vital to England's chances of success at the World Cup which start in Germany on June 9.
The 20-year-old, who has scored 11 times in 29 international appearances, limped out of Euro 2004 when he suffered a foot injury during England's quarter-final defeat by hosts Portugal.
Rooney cracked the fifth metatarsal, an identical injury suffered at the end of 2005 by fellow England striker Michael Owen.