The Hammers offered £14.5million plus add-ons for the Spanish striker but del Nido said that Sevilla were forced to reject it because they want the player to stay in Andalusia.
"He has four years left on his contract," del Nido told reporters.
"He is at home here. He has scored a lot of goals and delighted us with his football.
"The summer will tell us in due course if he will still be with us, but if you ask my opinion I'd rather there were no bids.
"West Ham offered €17m (£14.5m) in cash, with €3m (£2m) more in incentives, but we do not value the offer and the player refused."