Sir Alex Ferguson is waiting for the results of a scan on the thigh injury Michael Owen suffered at Old Trafford last night as the Manchester United striker faces up to another period on the sidelines.
The injury-plagued front-man was handed a rare start in United's 2-0 Champions League win over Otelul Galati.
Owen was involved in the build-up to Antonio Valencia's eighth minute opener.
However, in making a run to the near post, Owen suffered a thigh injury which convinced the former England man immediately that he would not be able to continue.
Owen was eventually replaced by Javier Hernandez and expressed his own frustrations on Twitter after the match.
Now in his third season at United, Owen was making his 52nd appearance, almost two thirds of which have been as a substitute.
However, he has been blighted by fitness problems since injuring his hamstring during a goalscoring appearance in the 2010 Carling Cup final and now there are fears over how long Owen will be sidelined for once more.
"We are assessing it this morning," said Ferguson.
"He is having a scan done but he won't be available for Saturday.
"Hopefully it is not too long but it is a killer because he has started the season very well. His performances in training have been terrific.
"We wouldn't have scored that goal if Michael had not made his run so it is a bit of a blow."
Ferguson also reported midfielder Anderson was a doubt after suffering a "knock" in the game.
There was no good news around England trio Ashley Young, Chris Smalling and Tom Cleverley, all of whom will miss Saturday's Premier League encounter with Sunderland through injury and will almost certainly not be involved in the Three Lions' forthcoming internationals against Spain and Sweden.
However, United will welcome back skipper Nemanja Vidic from his European suspension.