Everton boss Roberto Martinez says Chelsea target John Stones "is not for sale and that is the end of it".

An upbeat Martinez spoke at Thursday's pre-match press conference and reiterated his desire to hang on to one of his key players and stated Everton are "not a selling club".

Chelsea have made two bids for the centre-back Stones, the most recent for £25m, but Jose Mourinho shows no signs of giving up his pursuit of the 21-year-old, while Manchester United and Manchester City have also been linked with the England starlet.

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"I have said before the player is not for sale and that is the end of it," said Martinez. "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."

Meanwhile, Mason Holgate's imminent arrival from Barnsley, Stones' former club, for a reported initial £1m fee has already seen comparisons made with the England international but Martinez was keen to play those down.

"Mason, at 18, has already played 20 games in League One and that shows the potential he has," he said.

"We seem to have agreed terms with Barnsley and he will be a phenomenal young prospect coming into that golden generation we feel we have at the club and he will be a good one for the future.

"Mason is a completely different type of player to John but in terms of personality and character they are very similar."

Everton will also find out later on Thursday how long left-back Leighton Baines is likely to be out after he re-injured the ankle he had an operation on towards the end of last season.

"We will get the results [of the scan] and we will get a clear idea of the problem," Martinez said. "Because of the previous surgery he had in that area it is an extra sensitive part of his body so we need to make sure we are clear with the extent of the injury."