Chelsea's offer of £15 million fell short of AC Milan's £25 million valuation for the 29-year-old French goalkeeper. Despite this, Maignan is said to be growing frustrated with his current team.

According to reports, Maignan has given his current club an ultimatum. If AC Milan does not accept a suitable offer from Chelsea, he will leave the team as a free agent when his contract expires at the end of the next season.

Chelsea remains optimistic about reaching a deal with Maignan and is hoping to finalize the transfer before the FIFA Club World Cup.