Wayne Rooney will be out of action for up to three weeks, according to Manchester United boss Sir Alex Ferguson.
Rooney was left behind when the Red Devils flew out to Spain for Wednesday's Champions League encounter with Valencia.
The striker had struggled to shake off an ankle injury which led to his substitution in the second half of Sunday's Premier League draw with Bolton Wanderers.
Rooney's injury was not thought to be too serious, but Ferguson revealed at his pre-match press conference that the England striker is likely to be sidelined until mid-October.
He will now miss Saturday's league trip to Sunderland and also England's Euro 2012 qualifier against Montenegro on October 12.
"It will be two to three weeks," said Ferguson. "But it depends because Wayne has done quite well with his recovery from injury in the past."
Rooney has scored just one goal in five appearances for the Red Devils this season and Ferguson suggested last weekend that he was struggling to cope with the pressure that recent revelations about his private life had brought.
Meanwhile, Ferguson also confirmed that veteran midfielder Paul Scholes will be sidelined for around ten days with a calf problem.
However, Rio Ferdinand looks set to return from his knee ligament injury against Valencia as Ferguson looks to strengthen a defence which has leaked ten goals in seven games during his absence.
"It's a decision I'll take tomorrow," he said."He's had plenty of training and a couple of reserves games. He also played against Rangers and Scunthorpe but he's been out for five months.
"That's why I didn't risk him on Sunday against Bolton. I felt that would be a physical challenge so we decided to stick with Nemanja Vidic and Jonny Evans, who have done very well for us.
"I have no complaints about their performance levels."