However, if the Stamford Bridge outfit are unsuccessful with this bid, they are willing to make a record-breaking offer for the youngster, according to the Metro.
Rio Ferdinand is currently the most expensive English defender in history after his £30 million move from Leeds United to Manchester United in 2002 [via BBC Sport].
Chelsea were also involved in the priciest transfer of a defender, from when they sold David Luiz to Paris Saint-Germain for £50 million [Daily Mail].
Nonetheless, even a huge bid may not be enough to entice the Toffees in to selling the centre-back.
Everton are currently insisting that they will not sell the defender at any price, the Daily Express report.
The defender made 27 appearances for the Merseyside club last season, and he has fast become a regular starter under Roberto Martinez.
This appears to have enticed Jose Mourinho, but has also made signing the player far more difficult, as he could be a key player in Martinez’s future plans.
Chelsea already have John Terry, Gary Cahill, and Kurt Zouma to play in the middle of their defence, but with Terry now 34-years-old, new blood is perhaps needed.