Sarri's move for Martusciello will see the pair reunite at Stamford Bridge after spending time together at Empoli, prior to Sarri's departure for Napoli's top job in 2015.
It will not come as a surprise to many with Sarri being strongly linked to the Chelsea role for many months.More news: Senegal, Japan, Uruguay fans tidy up after team plays in World Cup
Sarri, 59, guided Napoli to a club record number of points in a single Serie A season last term, with their tally of 91 still four short of champions Juventus.
Brazilian central defender David Luiz had been snubbed by manager Antonio Conte and Gary Cahill's poor form meant that Chelsea had to utilize a young Dane called Andreas Christensen in the heart of the defence.
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Sport Italia are now reporting that not only will Sarri be announced at Chelsea very soon, but that his very first signing will be joining him at the same press conference.
His exploits over the last couple of seasons also make him a possible option as the focal point of attack, potentially making him an attractive short-term solution. The 31-year-old scored 22 goals in all competitions and provided 9 assists for the side as well.
Napoli, on the other hand, are reportedly looking to tie him down to a new deal once again in order to ward off suitors, or possible increase his transfer valuation.More news: Fans react on Twitter to Southampton ace Dusan Tadic's World Cup performance
In each of his two summers in charge, Conte tried to convince Chelsea to sign Belgium forward Dries Mertens.