Everton have completed the signing of teenage defender Mason Holgate from Barnsley for an undisclosed fee, understood to be an initial £1million.
Holgate, 18, has put pen to paper on a five-year deal, keeping him at Goodison Park until 2020.
But Everton have insisted Holgate has not been signed as a potential replacement for John Stones, who will not be sold to Chelsea, according to manager Roberto Martinez.
Martinez said: “I have said before the player (Stones) is not for sale and that is the end of it.
“Our situation has been very clear from the beginning. We are not a selling club who will lose our best performers.
“His performance at the weekend was very strong and for a young man to come up with that leadership is a real sign of what he is as a footballer.
“He is very important player for us and we are looking forward to seeing the best of John over the next few seasons, not just the next few weeks.”
England centre-back Stones has been the subject of two failed bids from Chelsea, the last worth £26million, but Jose Mourinho shows no signs of giving up his pursuit while Manchester United and Manchester City have also been linked with the 21-year-old.
Holgate is a product of the same Oakwell academy as Stones, who Everton signed from Barnsley for £3million in January 2013.