Lacroix is closing in on a move to Chelsea, and Crystal Palace have identified the 19-year-old centre-back as their solution, with an opening bid expected to land in Brittany within days.
Fulham have also registered an interest, though L'Équipe reports they are some way behind Palace in the process. Brest, for their part, are reluctant to let Le Guen go and are expected to hold out unless a substantial offer arrives, despite the player himself having reached an understanding with the London club.
Le Guen has made just six senior appearances since his debut last August, when he came on as a substitute in a 3-1 defeat away to Lens, but a run of late-season starts — including matches against Paris Saint-Germain and Strasbourg — was enough to convince Palace of his potential. He is under contract at Brest until 2029, giving the Ligue 1 club a strong negotiating position even with personal terms already in place across the Channel.
The move would extend Palace's recent record of recruiting French centre-backs, following the success of Lacroix himself and the emergence of teenager Jaydee Canvot since Marc Guéhi's departure in January. With four competitions to plan for next season, Palace are looking to add both depth and long-term quality at the back, and Le Guen's arrival — should it be completed — would represent a signing for the future rather than an immediate replacement for the outgoing Lacroix.
Standing at 6ft 6in, Le Guen's game is built around his aerial presence and his ability to defend crosses and long balls, attributes that stand out even though he only settled into central defence full-time in the past two years, having come through Brest's academy playing further forward.
He has also captained the club's reserve side, an early marker of leadership potential despite his limited senior experience. Palace are not relying solely on Le Guen to solve their defensive rebuild, with Augsburg's Chrislain Matsima also on the club's shortlist as head coach Pierre Sage weighs up his options this window.