Fabio Capello faces an anxious wait to discover if Wayne Rooney will be fit to play in England's vital Euro 2012 qualifier in Montenegro on 7 October.
The striker's hamstring injury forced him to miss Manchester United's draw at Stoke on Saturday, and he has also been ruled out of Tuesday's Champions League game against FC Basel at Old Trafford.
"It's difficult to assess on hamstring injuries," said boss Sir Alex Ferguson.
England need a point from their final group match to guarantee qualification.
Ferguson added: "We hope to have him back quickly. He (has done) a bit of jogging but that's all."
Ferguson and his England counterpart Capello will hope Rooney is ready to return in United's home game with Norwich City on Saturday and then join up with his international colleagues for the clash in Podgorica.
Capello will be keen to have Rooney at his disposal after the striker's brilliant start to the season.
Ferguson, meanwhile, admitted that United's recent failure in the final stages of the Champions League against Barcelona in 2009 and at Wembley this year means this cannot be labelled "a golden period" for the club in Europe.
He said: "I think the Champions League is the best competition in the world now, better than the World Cup and the European Championship. It's fantastic.
"It's not a golden period for us because we have lost two finals but I do think we have been consistent in the Champions League. I think our form away from home has been outstanding and obviously we now hope we can do better and win it because that's the aim of this club all of the time."
Ferguson, who will also be without Javier Hernandez against Basel after he suffered a dead leg at Stoke, gave encouragement to United's shadow strikers - led by Dimitar Berbatov and Michael Owen - that they will get opportunities throughout the season.
On Bulgarian Berbatov he said: "I don't need to reassure him. He knows he's part of the squad and it applies to many players. Federico Macheda, Mame Biram Diouf and Michael Owen have not played regularly. It's early doors - there is plenty of time."
One man who has played regularly, and quickly won Ferguson's approval, is Ashley Young. The former Aston Villa man has made a fine start to his United career after his summer switch.
"He's shown great awareness of the game and fantastic endurance going from box to box," said Ferguson. "This is something we have enjoyed with Ryan Giggs for many, many years.
"Ashley is also an outstanding crosser of the ball, really first class. He's integrated very well and his application in training has been good. He's done everything right and done very, very well."
Ferguson revealed he hopes captain Nemanja Vidic may be fit to return following a calf injury after the international break.