Chelsea manager Jose Mourinho has admitted his club have made a bid for John Stones and says any deal for the defender is in Everton's hands.
The Toffees are believed to have rejected a bid of around £20m for the 21-year-old, who played in Everton's 3-1 Barclays Asia Trophy final defeat to Arsenal on Saturday.
Mourinho said: "We made a bid because we like the player, we don't make bids for players we don't like - but I respect Everton. It's up to them - everything is in their hands.
"I don't speak about him (Stones) because he's not my player. We've made the bid and the bid is there. Everton have the power to accept or refuse the bid. This is a problem between John Stones and Everton.
"When the transfer window is open, every club and player is open to bids.
"Bids come for our players and we make bids for other players. The process can be so simple.
"I would advise Roberto Martinez to do the same thing I do. If I don't want to accept any offer, I say 'I don't accept any offer'. He can make it very, very easy.
Martinez expressed his frustration that news of the bid had become public.
"There is the disappointment of a club making a statement to the press and making it openly," he said.
"I don't think we'd do it and speak about a player. John Stones is an Everton player, full stop."
Stones said at a sponsor's event on Friday night: ''I am very happy at Everton."
And Martinez underlined his determination to hang on to his best players after dismissing speculation midfielder James McCarthy could be another of his players destined to leave Goodison Park for a bigger club.
He said on Saturday: "We're not a selling club in that respect."