Brentford are in talks to sign centre-back Bjorn Engels from Olympiakos, Sky Sports News understands.
The 23-year-old Belgian has emerged as the Bees' top target to replace John Egan, who joined Sheffield United last week.
Engels is a former Belgium U21 international and has three years left on his Olympiakos contract.
Reports in Belgium claim he is of interest to former club Anderlecht as well as Club Brugge, Standard Liege and Genk, after being told he can leave the Greek club.
He could become the Sky Bet Championship club's second centre-back signing this summer after Charlton's Ezri Konsa replaced Andreas Bjelland.
Brentford have made two senior signings so far this summer, also bringing in winger Saïd Benrahma from Nice to replace Florian Jozefzoon, who joined Derby County last week.
The Bees are also keen to bring in a box-to-box midfielder and young left-back before the transfer deadline.
Meanwhile, they are insisting to clubs that Ollie Watkins and Chris Mepham are not for sale this summer amid interest from Premier League teams.