Everton boss Roberto Martinez has accused John Terry and Chelsea of making an 'illegal' approach for defender John Stones.
The Toffees have already rejected respective £20 million and £26 million bids from the Blues for the England international during the off-season.
However, Jose Mourinho and several Chelsea players, including Terry and Gary Cahill, have openly discussed the club's interest in signing Stones.
Terry admitted on Wednesday the Premier League champions were looking at Stones as one for the future and his comments have raised the ire of Martinez.
"That is wrong; that is illegal," Martinez told reporters ahead of Everton's league opener against Watford on Saturday.
"The rules don't allow you to comment on players who are registered at other clubs in that open manner. That is disappointing.
"He is not for sale, we have said that many times, he is not for sale.
"I am not stupid enough to say I know what will happen, or that I have a crystal ball but I have always said John Stones is not for sale."