The Belgian forward is up for sale this summer at Chelsea and multiple clubs are keen on him.
He spent last season with Serie A outfit Roma and made 25-goal contributions in 47 appearances.
Now he is coming back to train with the Chelsea players who are not travelling with the first team for their pre-season tour.
Lukaku again joined the Premier League side back in 2021 but it did not go according to plan.
He spent his last two seasons away from Stamford Bridge on loan in Serie A with Inter Milan and Roma, respectively.
Now it remains to be seen if Chelsea will be able to offload the Belgian international before the new season starts next month.