But the Portuguese sees fan favourite Marcus Rashford literally growing in stature and expects him to score more goals this season.
Last month Real Madrid striker Ronaldo became disgruntled as he felt singled out for disproportionate treatment by Spanish prosecutors, who accused him of evading tax of €14.7 million.
Those allegations were denied, and Ronaldo was believed to have told those close to him he wanted to quit both the club and Spain.
That stance seems to have softened and talk of a summer return to United — the club where he made his name — has dissipated.
United boss Mourinho worked with his compatriot in Madrid and says an Old Trafford reunion was never on the cards.
“We have never thought about it because he is too much of an important player for his club, of great economic power,” he said.
“We have not been able to find for whatever reason anything that could have made us think that Ronaldo could leave. I am not a defender of my club once I waste time on players who are mission impossible.”
Mourinho gave a list of summer targets to executive vice-chairman Ed Woodward with the hope of making four top-quality additions.
United have so far brought in Victor Lindelof and Romelu Lukaku, with the latter’s arrival said to have ended their interest in Real Madrid striker Alvaro Morata.
“He belongs to Madrid,” said former Real boss Mourinho. “Madrid have decided and we have not come to an agreement. It is simple. It is a shame.
“He is a player who made it to the first team with me. We have a special liking for him, he is someone special. I enjoyed watching his evolution at Juventus and Madrid.
“It is like that. I don’t think he can end with us.”
Mourinho’s men kicked off their pre-season tour with a comfortable 5-2 win against LA Galaxy in Los Angeles on Saturday.
Marcus Rashford’s brace was complemented by a Marouane Fellaini strike in a one-sided first half, before Henrikh Mkhitaryan and Anthony Martial scored for a completely changed second-half team. Giovani dos Santos pulled back two late goals for Galaxy on a night on which Mourinho decided to deploy a three-man defence.
Rashford is not only growing as a player but in stature too, having bulked up and sprouted three centimetres over the past year. The 19-year-old looked sharp and is now a far more imposing presence than the player that burst onto the scene.
“It’s just the natural evolution of a kid,” Mourinho said. “Accumulation of minutes on the pitch and you change your body when you’re a young kid so that’s absolutely normal.
“He’s already taller than when I arrived 13 months ago, he’s three centimetres taller, and obviously he put on some muscle, but without any kind of specific work because his speed is the most important quality so we don’t want to lose that.
“Today he was in a different team than (Romelu) Lukaku. In this pre-season we will also try both in the same team which I think can also work.”
Playing big-money signing Lukaku alongside Rashford is a tantalising proposition, especially given the fact Mourinho expects the 19-year-old to find the net with more regularity this term.
“Last season... I think he was one of the top three with more appearances for the team so he played a lot, he developed a lot. He played in different positions, which is good for his evolution.
“Last season for too long he was in a period of not scoring goals and missing chances, which was not a drama because sometimes that’s part of the evolution. We knew this season he is going to score more goals than last season.”