Over the weekend, it was claimed that the Bees had emerged as the frontrunners for the sought-after 18-year-old, moving ahead of other Premier League clubs.
A price of £25.6m has allegedly been agreed between the respective clubs with Nusa due to spend the remainder of the campaign in Belgium.
However, it has been widely reported that knee and back issues were identified by Brentford's medical staff when assessing the prospect earlier this week.
The subsequent transfer is now in some doubt, it being claimed that Tottenham Hotspur are monitoring the situation in the event that an opportunity arises to sign the Norway international.
Head coach Ange Postecoglou insisted to reporters in a press conference on Tuesday that Spurs were unlikely to conduct any further business before Thursday's deadline.
Furthermore, the Evening Standard says that Brentford are currently not prepared to go through with their proposal for Nusa.
Brentford are said to be keen on further medical information regarding Nusa, who has come through 1330 minutes spread across 28 appearances in 2023-24.
The report suggests that the Premier League outfit are waiting to discover whether there is a willingness on Club Brugge's side to alter the financial terms in Brentford's favour.
There also remains the possibility of Brentford and other interested clubs scrapping their interest until the summer, with Nusa possessing a contract until 2027.
From Brentford's perspective, though, Nusa successfully coming through the rest of the season with no further issues may lead to increase competition for a player who has already represented Norway on four occasions.
Thomas Frank has been able to strengthen his squad this month with the acquisitions of Sergio Reguilon, Yunus Emre Konak and Hakon Valdimarsson.
As it stands, signing Nusa for £25.6m would represent a club-record outlay, yet funds will be generated through David Raya joining Arsenal on a permanent basis in July and the likely departure of Ivan Toney.