Everton manager Roberto Martinez says defender John Stones was not sold to Chelsea because the first offer made by the Blues came three weeks before the start of the season.
The England international asked to leave the club at the end of last month after the Blues made three bids of £20m, £26m and £30m.
But Everton rejected all bids for the 21-year-old, much to the delight of the Spaniard.
"There are moments when you can not replace players within the transfer window and it becomes damaging to lose players at the moment in the season," Martinez told reporters.
"That is why I feel so strongly that the window should not be open when the season starts. Maybe we need to be pioneers. If affects football all over the world.
"I have been involved in 10 seasons and I can tell you three cases in every window. There are solutions to be found.
"It is part of the rules. I have always been vocal in not agreeing with having the transfer window open but you are allowed to make enquiries and table offers. If there is interest in your players it is a compliment and shows we are doing something well.
"But we are clear in our strategy, building a young team and giving them big roles and that continuity is paramount. We have made progress in every window.
"Every player who represents Everton needs understanding and our best interests are to keep on developing John and that's exactly what we will keep on doing.
"He has been performing at a good level and has gone from strength to strength in a period of high pressure. He performed with a composure and maturity. He performed in a natural way."