The Belgian youngster signed for the Blues in 2011, but is already on his second move away from London.
Lukaku spent an impressive campaign with West Brom first time around, and is now performing well for Everton – who are firmly in the race for a top four finish.
However, Chelsea are thought to be ready to axe him for a decent offer in six months’ time.
There are rumours that Jose Mourinho and the powerful 20-year-old have a less than healthy relationship, and that the Portuguese coach doesn’t rate him as the sort of player capable of leading the line for the Stamford Bridge side.
It is also said that an offer in the region of £20m may be enough to convince them to sell as they look to mount moves for Costa or Falcao.
This news will catch the eyes of a number of Premier League sides, with Everton and Tottenham likely to be two of the more interested parties.
Mourinho is desperate to land a top class centre-forward, with Costa or Atletico Madrid and Monaco’s Falcao two of his major targets.