The Senegalese international, who has 24 caps for his country, had been in talks with Lazio over a proposed three-year contract worth €1.5m per season, including a €500,000 signing bonus. Dieng had been hoping to join the Italian capital club after his contract with Lorient expired at the end of the 2025-26 season.
Dieng's medical history, including concerns over his knee, had been known to Lazio before the tests took place. The player has previously played for Angers, Marseille, and Diambars in Senegal, and has experience playing at the highest level, including the FIFA World Cup.
The next step for Dieng remains uncertain, but it is clear that his proposed move to Lazio has fallen through.