The 21-year-old is not part of Enzo Maresca's plans for the 2024-25 season, but he failed to secure a switch to another Premier League team before the August 30 cut-off point.
However, English top-flight clubs have still been able to sell players to foreign leagues since the Premier League window closed, notably the Greek Super League and Turkish Super Lig.
A deal to send Fofana on loan to AEK Athens with a £20m buy option - which would have made him their most expensive signing of all time - was reportedly agreed, but the two clubs then hit a roadblock when exchanging documents.
Those issues could not be resolved by the time the Greek transfer window slammed shut on Wednesday, and transfer expert Fabrizio Romano now reports that the deal cannot be salvaged.
Chelsea 'still searching' for Fofana solution after AEK Athens collapse
Romano adds that the Blues are now scrambling to find Fofana a new club before other windows across Europe and the rest of the world close later this month, but they are running out of time to get a deal done.
Both the club and Fofana's entourage are working to engineer his exit as a matter of priority, as the Ivory Coast international is part of the undesirables squad training away from Maresca's first team at Chelsea.
The Blues paid £10.1m to bring Datro Fofana to Stamford Bridge from Molde in January 2023, but he has failed to make the grade in West London, making just four senior appearances for the capital giants.
The 21-year-old has been loaned out twice to Union Berlin and Burnley since arriving in the UK, but he only enjoyed moderate success with the latter, scoring four times in 15 appearances last season.
Datro Fofana agreed a six-and-a-half year contract when he joined the Blues in 2023, meaning that his current terms are not due to expire until the end of the 2028-29 campaign.
What next for Fofana after transfer collapse?
Regardless of what caused the AEK Athens deal to collapse, Chelsea must now work around the clock to offload Datro Fofana, who risks a few months out in the cold if he cannot secure an imminent switch.
The Turkish Super Lig transfer window is still open for another day, so it would not be a shock to see both Chelsea and Datro Fofana's camp offer his services to the likes of Galatasaray, Fenerbahce and Besiktas.
Galatasaray in particular have no need to bring in a new centre-forward, though, having pulled off the shock loan signing of Victor Osimhen while already having Mauro Icardi, Dries Mertens and ex-Chelsea man Michy Batshuayi in their ranks.
Alternative - and less desirable - solutions include a move to Serbia, Mexico, Israel or the United Arab Emirates, where the windows are still open; clubs in the latter can sign players until October 1.
However, if Chelsea cannot force Datro Fofana out of the door to a Turkish club in the coming hours, the striker could exclusively play for the Under-21s or not be seen on the pitch at all.