The 23-year-old has spent this season on loan at Birmingham, but the Blues balk at the striker’s price.
Birmingham will have to pay a pre-arranged fee of around £7.5million for the forward, according to the Daily Mirror.
Benitez has scored just three goals for Birmingham so far this season.
Birmingham chief Peter Pannu said: “We will know about Chucho’s future in due course.
“If we don’t exercise the option, then so be it. His club can then freely send Chucho to the North Pole or Bangladesh – anywhere.”
