Barcelona have made an official bid for Chelsea defender David Luiz, according to Sky sources.
The Spanish heavyweights have been linked with the Brazil international all summer and are understood to have finally made their interest formal on Wednesday.
But Blues boss Jose Mourinho has insisted the 26-year-old is central to his plans and the bid is expected to be rejected.
Speaking after his side's 2-0 pre-season win over AC Milan, Mourinho said: "David has come back with us fantastically and we have to use his quality.
"He has big self-confidence and self-esteem, especially when he comes up from the back with the ball."
Luiz signed a new five-year deal with Chelsea last September and has made over 100 appearances since joining from Benfica in January 2011.
He is currently recovering from a hamstring problem but Mourinho is hopeful he will be fit to play in Chelsea's final pre-season fixture against Roma on Saturday.
'We won't risk David Luiz (against Real Madrid on Wednesday night)," said Mourinho. "But Roma is the last match before the season starts, so I think he needs to play against Roma. But, if he's not able to, he's not able to."
He was also linked with a move to Manchester United earlier this summer as part of Chelsea's bid for Wayne Rooney.
Reports had suggested that, in addition to offering money, Chelsea were also prepared to let Luiz or Juan Mata move to Old Trafford in exchange for Rooney.
Chelsea subsequently denied any players were offered as part of the deal and Mourinho confirmed there was 'no chance' of Luiz leaving Stamford Bridge.
There has also been speculation that Bayern Munich, who are coached by former Barcelona boss Pep Guardiola, are interested in Luiz.
But Guardiola, speaking at a presentation before the Audi Cup in Munich last week, said he was happy with his defensive options.
Bayern have the option of dropping holding midfielder Javi Martinez back into defence now that Thiago Alcantara has arrived to fill a similar role to the one his fellow Spaniard had last season.
"He's not coming to Munich," he said. "We've got four or five central defenders.
"There is no truth to the speculation."