But a complicated transfer history means any deal for the 22-year-old will run through Marseille before it can be completed.
According to Fussball Transfers, four Bundesliga clubs have joined a growing queue of European teams tracking the Switzerland Under-21 captain at OH Leuven: FC Augsburg, TSG Hoffenheim, VfB Stuttgart and Werder Bremen have all watched him closely this season. Feyenoord, Everton, Ipswich Town, RC Strasbourg and Olympique Lyon are among the other clubs showing interest.
Nyakossi stands 1.94 metres tall and has drawn attention for a combination of physical dominance and technical quality that is unusual in a defender his age. He is comfortable stepping out of the defensive line, winning aerial duels, and playing progressive passes into midfield — attributes that make him well-suited to a high defensive line system.
The transfer complexity stems from his contractual history. Nyakossi came through the Servette academy before joining Marseille in 2022 for €2 million. He could not break into their first team and moved to Leuven in January 2025 for just €800,000 — a sale that included a sell-on clause and, critically, a buyback option for Marseille valued at only €6 million.
That clause is currently active and would give Marseille the right of first refusal on any transfer, at a price significantly below what Leuven believe they could command on the open market. Leuven are hoping to generate considerably more than €6 million from Nyakossi's sale — his contract runs until 2027 and is understood to be valued by the club at between €12 million and €15 million.
If Marseille choose to exercise the buyback option, any interested club would then need to negotiate with the French club rather than Leuven — a scenario that could either increase the final cost or complicate timelines.
Nyakossi has not yet represented Switzerland at senior level but has been a fixture in their Under-21 setup throughout this season. Leuven are prepared to sell but will push for maximum value in what they expect to be a competitive process.