Wigan and Bolton also want the 24-year-old, who has a clause in his contract allowing him to leave Bramall Lane if Sheffield United go down.
Chairman Terry Robinson said: "Everton are the favourites - it is Phil's preferred choice.
"If Sheffield United are reinstated, it's highly unlikely Phil will leave."
Robinson added: "If we're not reinstated, then he'll invoke the clause in his contract. If we're reinstated we wouldn't even be having this discussion."