The move for 20-year-old French left-back Daeyanne Metali from Toulouse to Sunderland is facing serious jeopardy.
The player has struggled to pass part of the medical assessments conducted over the last 24 hours. Consequently, he needs additional in-depth medical examinations and is returning to France.
This represents a significant setback for the Black Cats, who had agreed a record fee of £25.7 million (€30 million) and triumphed in the fierce competition against other Premier League and European clubs for one of the most promising full-backs in Ligue 1.
Medical staff at Sunderland identified complications during standard testing protocols, prompting an urgent suspension of the five-year contract signing.
The fate of the transfer will be decided following consultations with independent medical specialists and the hierarchy at Toulouse.
Sunderland's head coach, Regis Le Bri, was hoping to integrate the defender into the starting line-up for the upcoming league matches.
