Lyon have rejected Chelsea's request to bring Italian left-back Emerson Palmieri back to the club this January.
Chelsea hope to find cover for the injured Ben Chilwell, who is facing nine months on the sidelines following the decision to send him for surgery on a partially torn ACL.
As it stands, Marcos Alonso is the only natural left-back in Thomas Tuchel's squad, and attempts to use Reece James in the position in Wednesday's 1-1 draw with Brighton ended badly after he was forced off with a hamstring injury.
Lyon have the option to buy Emerson permanently at the end of the season and would have needed to agree to terminate his loan and give up that option. Whether they ended to sign him permanently is unclear, but Emerson has been a near-permanent starter in Ligue 1 this season and Lyon had no desire to let him go.
Dutch teenager Ian Maatsen is another candidate for a recall. The 19-year-old has impressed with Coventry City in the Championship, and it is believed that Chelsea would rather let him keep developing there than bring him back in January.
A new addition could be on the cards at sources have confirmed to 90min that Chelsea are looking at Everton's Lucas Digne, who has fallen out of favour with Toffees boss Rafa Benitez.
Everton have already agreed to sign Dynamo Kiev's Vitaliy Mykolenko in January, paving the way for Digne to leave, but Chelsea do not want to spend too much money on the Frenchman and would prefer a loan deal.
Elsewhere, reports have linked Chelsea to AC Milan's Theo Hernandez and Barcelona's Sergino Dest, who is a right-back but is comfortable on the left as well.