Eighteen-year-old striker Rashford made a remarkable impact for United last season. He only made his first-team debut in February but finished 2015-16 with eight goals and was rewarded with a surprise spot in Roy Hodgson’s England squad.
After netting on his international debut in a friendly against Australia, he was then limited to two late substitute appearances at Euro 2016, where England crashed out to Iceland in the last 16.
Hodgson has been replaced by Sam Allardyce and Rashford was named in Gareth Southgate’s England U21 squad this week.
Mourinho said: “I prefer it this way, because to be selected (for the seniors) and be on the bench behind (Harry) Kane and (Jamie) Vardy and all the experienced players, and play one minute or not play...
“I would prefer him to go to the U21s and play what Southgate decides, but I believe 90 or 80 minutes, a big part of matches, and contribute to his development.”
Rashford ended up making 18 appearances — all of them starts — last season under Mourinho’s predecessor Louis van Gaal.
This term his only action so far has been as a substitute in the Community Shield, while new frontman Zlatan Ibrahimovic has come in and netted four goals in three starts.
But Mourinho insists Rashford, who he has described as “amazing” for his age, has a bright future at United and will play “a lot”.
The Portuguese said: “Marcus is a young and talented player. We bought one striker (Ibrahimovic) — not two or three or four. If you don’t trust him or want him to play, you buy other strikers. That is not the case.
“Zlatan is playing and is showing why, and Marcus is our striker number two at the moment. For an 18-year-old boy, I think he is amazing.”
Ibrahimovic’s fellow new signing Henrikh Mkhitaryan is another yet to start a game so far this term, coming off the bench in the three so far — the Community Shield and then Premier League wins against Bournemouth and Southampton.
Mourinho has defended his decision on that front and says his confidence in midfielder Mkhitaryan is such that he does not need to rush his integration. “It’s difficult but if (Juan) Mata is on the bench, you tell me I want to kick him out and want to sell him,” Mourinho said.
“If I don’t play (Anthony) Martial it’s because he is in crisis, or if I don’t play Ashley Young, it’s because I don’t like Ashley Young. If it’s Memphis Depay, it is because he is on his way out...
“It is because I think the others (starting ahead of Mkhitaryan) are playing really well.
“When some managers buy players they play them for sure because they think about protecting themselves — ‘I bought this player, I have to show the world I was right.’
“No — the first thing I think about is my team, not myself.
“Because I know he is a super player and I know for sure he will succeed, I am not in a hurry to say he plays every game now from the beginning, to show everyone how good he is. No.
“But he is ready to play and maybe he will play tomorrow (in United’s away league clash with Hull).”
Mourinho has emphasised it will be “very difficult” for Bastian Schweinsteiger to play for United this season.
Schweinsteiger has been frozen out of the first-team picture at United this term, with boss Mourinho making it clear he is not part of his plans.
When asked if there was any chance Schweinsteiger could play for United at all this term, Mourinho said: “I think it’s very difficult to happen.
“We have five players for two positions. It’s very difficult that an opportunity will arrive.”
Mourinho intends to treat the Europa League with the respect it deserves.
The Red Devils were handed a trip into the unknown after being drawn against Ukrainian side Zorya Luhansk in the Europa League.
However, they will also come up against familiar faces at Fenerbahce, who have former United striker Robin van Persie and ex-Liverpool defender Martin Skrtel in their ranks, while Dutch opponents Feyenoord also have former Liverpool men in forward Dirk Kuyt and goalkeeper Brad Jones.
“There are groups in the Champions League that are very similar, so it is good for that,” Mourinho claimed.