Mourinho has invited Lampard to return to Chelsea as his assistant manager after admitting that letting the midfielder go was one of the most difficult acts of his career.
He said: "You can't imagine how difficult it was. I think only Frank knows that, but at the same time I can feel some happiness about the process because, for sure, he comes back to Chelsea.
"For sure. Everybody wants it. Mr Abramovich - the No 1, the most important person - wants Frank to be back very much, I want him to be back and the staff want him back, so he comes back for sure.
"He can come back the way he wants. Mr Abramovich has left the door completely open for him on the understanding Frank can do anything he wants at this club. To repeat Mr Abramovich's words, 'He can come back the way he wants'.
"He can be a coach, he can start at the academy, he can start being my assistant at the same time because he is doing his coaching badges, or he can start in a different role.
"He will be back, hopefully for many, many years, because he's one of the most important players in the history of Chelsea."
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