Chelsea's deal for new goalkeeper Edouard Mendy is currently being held up by Rennes, who have made a last-minute demand to include Fikayo Tomori in the deal.
Mendy is set to become Chelsea's seventh signing of the summer, with reports stating that they had agreed a £25 million with the Ligue 1 side.
However, Rennes are now demanding Tomori on loan as part of the deal, in order to squeeze as much as possible from Chelsea.
Tomori, who has been linked with a loan move away from Chelsea in recent weeks, has fell down the pecking order even more with the signings of Thiago Silva and Malang Sarr, with the latter still looking for a club to take him on loan.
Tomori has also been linked with a loan move to Everton, yet Rennes are now the favourites to take him on loan.
Due to the negotiations taking a lot of time to be completed, Mendy has returned to full training with Rennes in order to maintain his fitness levels ahead of his move to Chelsea.
Previously, Rennes had tried to get Olivier Giroud as part of the deal for Mendy, yet this was immediately rejected by Chelsea.
Mendy was pulled out of training on Friday, and was not in Rennes' team as they won 4-2 against Nimes on Sunday.