Scott Parker admitted he is fearful that captain Tom Cairney could miss the remainder of the season.
The 30-year-old has not featured for Fulham since their 1-1 draw at Newcastle in December and has been struggling to return to full fitness due to an ongoing knee problem.
"You're getting to that point in the season, you're also getting to that point with Tom where he's been out for some time now and the issue is still ongoing," the Fulham boss said.
"So, of course there's that fear, definitely (that he could miss the end of the season).
"We are confident and what brings us that confidence is that he is close. He has managed to be able to train, come off it, train, come off it.
"But this is an ongoing issue and time is against him with nine games to go. We're still hoping that we can get a fit Tom Cairney on the pitch."
Parker has said before that they were pursuing multiple treatment options for Cairney, including a laser treatment, and announced on Thursday they would be looking at injections on the recommendation of a specialist.
Fulham host Leeds on Friday in the last game before the international break, but Parker said Frank Anguissa and Mario Lemina will not be away for the full time, with their respective nations Cameroon and Gabon due to play in red-list countries.
"It's not ideal in the current situation, players travelling," Parker said.
"But at the same time, there is a big tournament and the managers that are involved at that level, in terms of managing their countries, they need that time to prepare for what are big tournaments in the summer.
"On a selfish note, from my point of view, of course it's not ideal. We've got a massive run-in now, we have had a lot of games. Players (will be going) all over the place and the situation we are in, the pandemic, there are a lot of rules, regulations when they come back from the countries they are going to. It's a constant fear and a worry.
"But on the flipside I also understand if you are a manager of a country, you need time to prepare. Come the summer it will be you under scrutiny, it's going to be you that's in the spotlight. These are the moments you need to prepare and work out the best way to go. It's catch-22 really."
He added: "The players that have games in red-list countries won't be playing in those countries. We've got two.
"Those players would then miss 14 days and two Premier League games. It's just not feasible for a club like us to be able to do that. So they won't be playing in those countries."