Despite his decision to turn his back on a move to Spurs the winger may yet attract other clubs from the Premiership and Blackwell says United could still start next season without him.
According to the Yorkshire Post, his future is in doubt following a boardroom dispute over whether he should be sold. Chairman Gerald Krasner and managing director David Richmond have stated he is not for sale but fellow director Simon Morris is keen to attract the best offer.
Blackwell is in charge of the side for the final game of the season at Chelsea tomorrow and he admits he will take time out to talk with Milner about his future. "I shall discuss the position with James and I shall tell him what I think is best for his future," he said.
"He is a lad who has a bright future and I think he knows where he is going, he is strong enough to make his own decisions. Playing in Division One may well provide a decent learning curve.
"There could well be aspects of the game for him to learn in the Football League but at the age of 18 he has achieved so much already and it is no wonder top clubs are trying to sign him.
"The season has not even finished yet and we are talking about Tottenham coming in for him. They have made a brave decision to offer big money for James but it may just be that James does not want to go to London. It does not mean he might not want to go somewhere else and therefore, even at this stage, there is a chance we might not have James Milner next season."