Tottenham manager Mauricio Pochettino has suggested Erik Lamela may not play again this season.
Lamela has not featured for Spurs since October 25 as first a hip problem and then a family accident involving his brother kept him on the sidelines.
The winger even returned to his former club Roma in January for treatment on his injury but, despite being back for more than a month, a return to action is still not seemingly close.
Pochettino said on Friday that Lamela is now "100 per cent" recovering in London and his problem is purely a physical one, rather than anything personal.
But the Argentinian was less clear on when Lamela could next play for Tottenham.
"I don't want to lie to you and give some information that after you use, and you are right to use, but I can't say one, two weeks, three weeks, one month or maybe next season, I don't know," Pochettino said.
"It's too difficult my position because we are assessing him every day, how he is in the morning, we prepare a plan, sometimes he is involved from the beginning in the warm-up with the team, sometimes he feels pain, we change the plan.
"Now it is day by day and we see. We hope he can be available again as soon as possible as that is our idea but we can't give any more information."
Lamela is one of two absentees for Sunday's FA Cup quarter-final against Millwall, with Danny Rose still nursing a knee injury. Tottenham have said they expect the defender back in April.
Millwall will offer a stern test at White Hart Lane as they look to extend a remarkable run that has already included three Premier League scalps in Bournemouth, Watford and Leicester.
The League One promotion hopefuls are unbeaten in 17 games and have conceded just one goal in 10.
"We are very focused because the game will be very tough," Pochettino said.
"It is another London derby and we were watching all the games and they fully deserve to be in the quarter-finals.
"They were better than the Premier League teams. We are aware about that situation. We respect them. It is clear how they play, very compact, clear in their idea how they manage the game."
Police are on a high alert for the fixture, particularly after Millwall fans caused a stir by taunting Leicester's supporters following their victory in the previous round.
There is also a history of animosity between the two London clubs, after violence erupted around a pre-season friendly in 2001. Pochettino has called for calm.
"For me it is the first time I face Millwall, I hear a lot of things but I hope and wait until all happens in a really good way," Pochettino said.
"I hope nothing happens. I trust that our fans and their fans they behave well, that is my wish because it is football.
"Football is to try to enjoy and for happiness and there is no sense to fight for anything but in my head it is about being calm and enjoying football. That is my wish."