Lamine Camara will be staying at Monaco after the Senegal midfielder’s £47.1m move to Chelsea collapsed.
The 22-year-old had already completed a medical with Chelsea but his switch fell through shortly after the 23:00 BST deadline.
They had two bids rejected by the Ligue 1 side before Monaco eventually lowered their asking price when Folarin Balogun’s move to Everton came into renewed doubt.
Chelsea made their move for Camara in an attempt to bolster midfield options with Enzo Fernandez closing in on a joint-British transfer record £125m switch to Manchester City.
They had also held talks with Roma’s Manu Kone and another unnamed Premier League option.
One of the club’s aims this summer was to emerge from the transfer window with a stronger squad despite selling Fernandez to a direct rival.
Chelsea believe they have achieved that after signing Morgan Rogers from Aston Villa in a club-record £117m deal, centre-back Maxence Lacroix from Crystal Palace and, most recently, goalkeeper Emiliano Martinez from Aston Villa.
The club have also recruited strikers Emmanuel Emegha and Danny Welbeck, winger Geovany Quenda, midfielders Jordan Henderson and Valentin Barco, as well as full-backs Marco Palestra and Pep Chavarria.
No explanation has been given, although sources with knowledge of the situation believe the development may be linked to Everton’s proposed move for United States international striker Balogun.
Everton maintained throughout deadline day that talks were ongoing despite reports casting doubt over Balogun’s medical.
While some reports suggested the deal was off, Chelsea made progress in negotiations for Camara having previously struggled to reach an agreement with Monaco.
