Everton manager Roberto Martinez understands he will have further fights to keep John Stones, but insists the defender is at the "perfect" place.
Stones, 21, stayed at Goodison Park despite handing in a transfer request after ongoing interest from Chelsea, who had numerous bids rejected.
Martinez said the decision to keep the England international was based on what Everton needed in 2015-16, with a fight for Stones set to be ongoing.
"At the moment you are not making a decision only to delay it for another window. You don't do that. 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?" he said.
"Clearly, it's that John is in a perfect position to be important for how we want to play now. We have very young players ready to kick on like Ross Barkley, Romelu Lukaku and John Stones. It was about keeping that core.
"You go from window to window and you say, 'Will we finish as a stronger squad?' You assess. Players have moments of form, you look at their ages."
Martinez again lauded chairman Bill Kenwright for not jumping at the chance to cash in on Stones, who joined the club from Barnsley in 2013.
The Spaniard said Stones was capable of being England's best ever central defender.
"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," Martinez said.
"I'm going to be biased but I see John Stones as potentially the best centre-back that England has ever produced."
