Joachim Andersen has suffered ankle ligament damage and is set to be out for at least a month.
The new centre-back got injured barely a few days into training – and will have to wait until at least November to make his Fulham debut.
The most expensive Danish player ever when signed by Lyon at the start of last season was expected to feature alongside the likes of Manchester City recruit Tosin Adarabioyo at Sheffield United this weekend, but that hope has been dashed.
Head coach Scott Parker, when asked how long Andersen would be out, said: “The foreseeable future.”
Meanwhile, Kenny Tete has a torn calf and is also taking his turn on the treatment table, while Sunday’s clash with the Blades is a “game too soon” for midfielder Harrison Reed, Parker says.
The one ray of light is Mario Lemina’s expected return to the squad.
The Southampton loanee has been ‘training the full 10 days” since the start of the international break and is pencilled in for Parker and Fulham’s attempt at getting a first point on the Premier League board.