Lampard took over from Maurizio Sarri in July after just one year as a head coach with Derby in the Sky Bet Championship.
Mourinho managed Lampard across two spells at Stamford Bridge, helping the midfielder to become the club’s all-time leading goalscorer.
“One thing is the player, another thing is the manager,” Mourinho said. “The player, I don’t think any Chelsea fan will disagree with me if I say is one of the top five most important players of Chelsea history, and probably some will say not top five, maybe top three.
“Another thing is his managerial career, one year of experience in Derby where he showed good qualities and now he has Chelsea in his hands.
“He plays for big things. He plays Champions League, he played a European Super Cup, he had already big matches in his hands, and he has to grow up with the level of experiences, which I believe he can because he has huge experience.”
“I cannot separate from the fact that football has been always in his life. He was born son of a player, he grew up [nephew] of a football manager, he became a player, he became a top player… I think he has all the conditions to succeed.”
Lampard has endured a testing start upon his return to Stamford Bridge, with Chelsea winning just one of their opening four Premier League fixtures, and losing the UEFA Super Cup final to Liverpool.
The 41-year-old now faces the additional challenge of contending with a congested fixture list, as his side travel to Wolves on Saturday, before a Champions League game against Valencia on Tuesday.