Southampton boss Nigel Adkins says captain Adam Lallana will miss Saturday's match at home to Sunderland.
But Adkins declined to reveal Lallana's expected return date or give any further details of the injury.
The midfielder limped off during the first half of the 1-0 defeat of Reading on 8 December and there has been no official word yet on the severity of the problem.
Speaking on Thursday, Adkins said: "Adam is still in his knee brace. He is progressing well and is now off the crutches.
"He won't be available for Saturday's game against Sunderland and that is all I need to say."
Pressed for more information, he added: "We're just going to say he is out for the Sunderland game and you can ask me the next question ahead of the next game. That is all we are going to say."
In any case, Adkins is confident that Southampton have the players to cope without their skipper.
"Adam is obviously the captain and an instrumental character," said the boss. "He has got in the England set-up this season but we've got other players as well.
"Gaston Ramirez played ever so well there there when we played Reading, but we've got several players who can play in that position as well.
"Like all teams, you are going to suffer from injuries at certain stages, and it is how well you can deal with it.
"I believe we have got several very good players who can play in offensive positions, especially where Adam plays."