But Mourinho is not concerned and believes it is more important for the youngster to play rather than sit on the bench.
"The situation with England is funny because when you are 18 years old and are in the Under-21 national team, I don't think it's a drama," Mourinho told MUTV.
"I think he's fantastic, I think he's very good.
“But to be honest, for his development, I think it's better to be in the Under-21s and play two international matches than go to Slovakia with the first team and sit watching Harry Kane and [Jamie] Vardy and those experienced players that Sam is going to select.
“So I think it's very good for him at the age of 18 to play in the Under-21 national team.
"To be, at this moment, Manchester United's second striker [in the No 9 position behind Zlatan Ibrahimovic] – not the third or fourth or fifth – behind one of the top players in the world, who he can learn so much from, I think his situation is very good."
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