Chelsea have splashed cash for the Spanish defender with Duffy loaned to Fulham.
Chelsea have completed the signing of defender Marc Cucurella from Brighton.
The south coast side will receive a club record fee for the Spanish defender, who spent just one season with Graham Potter's side.
Chelsea boss Thomas Tuchel explains why he was so keen to complete the deal:
Also departing Brighton today is Republic of Ireland defender, Shane Duffy.
Newly promoted Fulham will be Duffy's home for the coming season.
Leicester manager Brendan Rodgers says the club has no intention of selling Wesley Fofana and James Maddison.
The pair have been subject to interest from Chelsea and Newcastle respectively.
Rodgers has made his message clear:
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