Fikayo Tomori is weighing up interest from Everton who are keen to take the defender on loan.
The Blues have revived their attempts to sign the 22-year-old after failing to strike a deal with Chelsea last summer.
Tomori was ready to move to Everton on loan but a last minute U-turn from the Stamford Bridge side, following the sale of David Luiz to Arsenal, scuppered hopes of the transfer being completed.
Everton started last season with only three senior centre-halves after a lengthy pursuit of Kurt Zouma came to nothing and then hopes of landing Tomori on loan were dashed late on in the window.
Reports of the centre-half being ready for a Blues medical are premature, and no deal has been agreed between the two clubs, but there is confidence that Everton will bolster their backline with the signing of Tomori.
The England international has interest from elsewhere but the Blues hope their long-standing admiration - and their efforts to sign him last season - will work in their favour.
Adding a centre-back to the squad has become the focus for Everton's power-brokers in recent days, in the wake of the toe injury picked up by Mason Holgate.
The full list of Everton's transfer business this window
Carlo Ancelotti is expected to provide an update on the extent of the issue at today's press conference but there are growing fears the 23-year-old faces an extended spell on the sidelines.
Yerry Mina is returning to full fitness after missing the end of the season and is expected to start alongside Michael Keane at Tottenham Hotspur on Sunday, in the opening game of the campaign.
Lewis Gibson, who is still expected to go out on loan to Huddersfield Town, and Jarrad Branthwaite provide back-up.
Everton, meanwhile, are not currently in pursuit of Napoli winger Hirving Lozano. Reports had emerged on Wednesday that the Blues were preparing a loan offer for the Mexican wide-man who was brought to Europe by Marcel Brands, when he was at PSV Eindhoven.
The Blues are focused on adding to their defensive options and still need to offload a number of fringe players before the close of the window.
