Lampard, who is beginning the final stage of his UEFA coaching qualifications, turned up two days late for a recent study trip in France with the FA's new Pro Licence candidates, fuelling speculation among other attendees he was in urgent meetings to facilitate his way back to Chelsea.
Despite signing a three-year deal last July, he will become the ninth full-time manager to leave the club under Chelsea owner Roman Abramovich.
Frank Lampard spent 13 years at Stamford Bridge, clocking almost 650 appearances and making a name for himself as one of, if not the greatest player in the history of the club.
Lampard has spoken previously about his desire to manage Chelsea.
Nevertheless, Lampard still impressed in his role as Derby's head coach, and Chelsea are now ready to hand him one of the biggest jobs in English football.
Lampard is the clear and obvious frontrunner to replace the Italian, having spent the first year of his managerial career with Derby, where he narrowly missed out promotion to the Premier League in the playoff final. Yet the opportunity to take the reins at the club he joined for £11m from West Ham 18 years ago on Friday would surely still be hard to resist. The Italian, who was secured from Napoli, was close to being sacked this year after results deteriorated dramatically following a promising start.
Juventus Director of Sport Fabio Paratici travelled to London to this week to negotiate Sarri's departure with Chelsea.
The goal-scoring midfielder would be well placed to work with Chelsea's crop of talented youngsters then, who would likely be handed extra first-team chances should that transfer ban be enforced.
Cristiano Ronaldo is understood to have given his blessing for Sarri to succeed Allegri at Juventus.