Chelsea's hopes of swiftly appointing Maurizio Sarri as Antonio Conte's successor have been affected after allowing the deadline governing the €8 million release clause in the Italian's contract at Napoli to expire on Thursday.
Sarri had emerged as the clear first choice to replace Conte, who is demanding to be sacked by Chelsea rather than resign and lose the money he is due from the final year of his own contract, reported to be in the region of £9m.
Despite appointing Carlo Ancelotti as Sarri's successor earlier this month, Napoli chairman Aurelio De Laurentiis is refusing to release the Italian from the final two years of his contract and instead demanded that Chelsea meet the clause to buy him out.
Chelsea, unwilling to commit big money to a new head coach as well as paying compensation to Conte and his large backroom team, declined and Sarri's lawyers are now exploring ways to extricate him from the deal, according to reports in Italy and England.
Unless a legal resolution is found Sarri's fate remains in the hands of De Laurentiis, and Chelsea are likely to find any further talks with Napoli are more complicated and tense as a result of their refusal to activate the clause.
Alternatives to succeed Conte are being explored, with former France coach Laurent Blanc and ex-Blues boss Avram Grant reportedly emerging as candidates for the role.
Allowing the managerial situation to drag on could have adverse consequences for Chelsea, who are attempting to tie key players Eden Hazard and Thibaut Courtois to new long-term contracts amid interest from Champions League winners Real Madrid.
Both players publicly stated after lifting the FA Cup earlier this month that they would not commit to staying at Stamford Bridge unless the club invest to close the gap on the domestic and European elite this summer, and the issue of Conte's replacement is also likely to influence their thinking.
Pepe Reina, who played under Sarri at Napoli and has too left the club, heaped praise upon his former boss.
"He is the main person responsible for all the Napoli records that he has broken in the past three years and of the team's great play," Reina told Diario AS.
"We have similar characters and we had a father-son relationship. I love him a lot and I will also be eternally grateful to him."
Reina described working under Sarri as "a spectacle," and added that he has his recommendation for any side.
"I would recommend him to any team in the world," he said. "For his football ideas and his compulsive way of working."
Rumours are still rife that Sarri will join Chelsea after one of his fitness coaches posted a photo on Facebook saying they are enjoying the sun, then with an emoji of a plane with London written next to it.