Fifa has told Chelsea that they cannot recall any players on season-long loans as part of their transfer ban.
The Blues were suspended from signing players for the next two transfer windows by Fifa earlier this month after they breached rules to sign Lens youngster Gael Kakuta.
Chelsea are appealing, but they had hoped they could minimise any damage by recalling the likes of Michael Mancienne and Scott Sinclair, who are on loan at Wolves and Wigan respectively.
But Fifa has told them that they definitely cannot have Sinclair back, while they will need to rule on Mancienne as Chelsea have an emergency-recall clause inserted in his agreement.
Another loanee Franco Di Santo - who is at Blackburn - could return to Stamford Bridge as he only moved on a half-season deal.
"If it's a season-long loan, it cannot be terminated in order to bring players
back," said a Fifa spokesman.
Chelsea are yet to get Fifa's full ruling on their transfer ban but that should arrive before the end of the month, after which point they will have 21-days to respond.