Everton boss Roberto Martinez expects further battles to keep hold of John Stones after fending off interest from Chelsea during the off-season.
The Blues had numerous bids for the England international centre-back rejected and the Toffees were determined to keep hold of the 21-year-old.
However, Martinez does believe there will be a lot more interest in Stones as he continues to develop and improve.
"At the moment you are not making a decision only to delay it for another window. You don't do that," he said ahead of the clash against Chelsea this weekend.
"You make a decision based on what do we need now, can you replace a player now, can we get a stronger squad by losing a player now?
"Clearly, it's that John is in a perfect position to be important for how we want to play now.
"There is a right time and wrong time and right way and wrong way in assembling squads and our squad at this point needed John Stones to be at the football club.
"I'm going to be biased but I see John Stones as potentially the best centre-back that England has ever produced."