Louis van Gaal has said that Manchester United had to sign Anthony Martial now to stop him becoming even more expensive.
The 19-year-old became the costliest teenager in the history of football when he joined United from Monaco on transfer deadline day for a fee of £36 million, which could rise to £58.8 million.
And Van Gaal himself described the fee as "ridiculous" earlier this week, but claimed on Friday that Martial could have been the £68 million man if United had waited another year.
"I have said to Ed [Woodward, United's executive vice-chairman], he is the best of his age and we need a striker in the future so we can wait a year and he is £10 million more expensive or now we can build him up," Van Gaal said in a news conference.
Van Gaal urged United supporters to be patient with Martial as he pointed out that rather more experienced players have struggled to adjust to life at Old Trafford.
"I can imagine the fans shall think [that for] £50 million he has to score," Van Gaal said. "No, no. He is 19 years old so he has to adapt. It is very difficult to adapt. You have seen how [Angel] Di Maria has struggled and he was 27. And [Radamel] Falcao, he was 29. So it is not so easy, especially at Manchester United. The pressure is much higher than at another club.
"So I don't think we have to give him too much pressure, but of course he has to adapt to our culture and our philosophy and that is difficult enough and maybe he can show signals of his quality in this season."
Van Gaal explained his decisions to loan out Adnan Januzaj, who has joined Borussia Dortmund, and James Wilson, who is set to sign for a Championship club, as he insisted both youngsters still have a big future at Old Trafford.
"I have said to Januzaj: 'I give you opportunities in the No. 9 and No. 10 position and then I have decided it is better for you to go to another environment and maybe you play more with them than me and we can see if you develop more in another environment.'
"It is the same as I have said to James Wilson, only James has to go to a Championship club because then I can call him back if my striker is injured and he has more playing time.
"For him, another year the same as last year is not good for his development. The same for Januzaj. That is why we don't sell because I believe in the quality of Januzaj and Wilson."