The Liga champions are believed to have lodged a €25 million bid for the 26-year-old on Wednesday in a bid to solve their defensive problems after missing out on Marquinhos and thwarted in their attempts to sign Thiago Silva.
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"If [Barcelona] need a central defender my advice is that they have to go to the second name they have in the list because they are wasting their time," Mourinho told the club's official website. "No chance."
Luiz and Juan Mata, who has also been linked with a move away from Chelsea this summer, both sat out the 3-1 pre-season defeat to Real Madrid in Miami on Wednesday through injury, and Mourinho feels their absence was missed.
"They are important players," he added. "The team with David Luiz and Mata is a better team. But we don't risk players in pre-season.
"Mata had a little thing, no risk, David has something from the past, an injury he had before the Champions League final, so we stop, we are not here to risk. But the team with them is a better team."