And the club are also expecting enquiries to land for key attackers, amid their shock move for Morgan Rogers.
Chelsea are attempting to get new boss Xabi Alonso well prepared for the new season but face challenges as pre-season gets underway.
Fernandez returns from the World Cup with his reputation more polarising than ever after a controversial tournament that culminated in a red card in the final - and fresh uncertainty surrounding his club future.
Chelsea value him at over £110 million and have expected a battle to hold on to him ever since his head was turned by La Liga interest last season. Real Madrid are publicly stating they are not going to make any offer for the player, and sources say the reason around that is that his price-tag is too high.
But Spanish neighbours Atletico Madrid are now coming into the picture as a potential landing spot for Fernandez if he is determined to push for a move away from Chelsea.
It could become an intriguing option for Fernandez. Chelsea insiders have maintained a stance that the club are not actively looking to sell him, but our sources understand they have continued to scope out the market for potential new signings in the centre of midfield.
Among the targets to have been looked at are Bournemouth's Alex Scott and Crystal Palace's Adam Wharton. But it is also believed they have an eye on Roma's Manu Kone, who has been assessed as an option by rivals Arsenal and Manchester United.
Chelsea have already caused a stir in the market this summer with their £117 milion move for Rogers from Aston Villa, who was undergoing his medical on Monday.
But Chelsea are determined to make a mark and improve under Alonso, and key detailing around that involves having a refined and focused squad in place by the time they face Fulham for their opening game of the season.
The Fernandez situation is very central to how things play out - but the Rogers signing could have a knock-on effect.
Chelsea are also beginning to anticipate interest from Premier League rivals in both Pedro Neto and Jamie Gittens, leaving the club with important decisions to make over whether they are prepared to sanction any departures.
The Blues have already signalled a willingness to listen to offers for Alejandro Garnacho and Nicolas Jackson this summer, but further exits will depend on how the window develops.