With the Euro 2016 contingent - including the likes of David de Gea, Wayne Rooney, Chris Smalling and Anthony Martial - resting, Mourinho's Red Devils bow was always likely to be a soft start, though second-half strikes from Will Keane and Andreas Pereira guaranteed a 2-0 win at the DW Stadium.
Everything about the 90 minutes was low key - from Mourinho's comfort-first leisure wear to his use of 22 different players - but the Portuguese admitted to being taken aback by the level of support he and his side received.
Around 7,000 United fans turned out for the gentle workout, unanimously roaring their support for a manager who is keen to pay them back after three relatively lean years under David Moyes and Louis van Gaal.
"I'm very happy, the result obviously is not the most important thing but it is always important," he told MUTV.
"Best of all was something that I never had before which was a friendly match, which I could call a training session against opposition, and I never saw something like this...so many supporters.
"They gave permanent support to the team, the manifestation of happiness about a few things they could see in the team, which was absolutely fantastic.
"If it is like this in a friendly match, like I said in my presentation, I will try to give them everything and I'm sure they will continue to give amazing support to the team."
Mourinho gave debuts to summer signings Eric Bailly and Henrikh Mkhitaryan, who arrived at a cost north of £55million, and saw plenty to please him.
Mkhitaryan was one of seven players replaced at half-time but in his 45 minutes on the pitch the former Borussia Dortmund play-maker showed more than enough to get excited about.
He moved nimbly in the space behind the striker, passed cleverly and teed up one great chance for Memphis Depay at the far post.
It was still 0-0 by the time he departed the scene but United fans appear to have a player who can provide an injection of colour after the monochrome Van Gaal years.
"Mkhitaryan is a top-class player and currently at the best stage for a footballer - 27/28 years old," said Mourinho.
"He is magnificent the way he thinks about football, he thinks very quickly and it's so sweet how he touches the ball
He can play in different positions behind the striker
He doesn't have the sharpness yet but his performance was very positive."
Bailly was given 82 minutes at the heart of defence, partnering Daley Blind in the first half and Phil Jones in the second.
The 22-year-old Ivorian had a relatively quiet afternoon, and effectively extinguished the fire of Northern Ireland striker Will Grigg, but seems destined for a major role at Old Trafford.
"With Eric, the way the fans showed how much they liked his performance when I changed him is enough," Mourinho added.
"Of course he is a very young boy coming from a very different environment, but you could see what he is at this moment
I will give him everything to try to make him better and better like I did with other central defenders I've had in my hands
He has showed the potential we saw when we decided to buy him."
United's preparations step up a notch on their forthcoming tour of China, where they face Dortmund, Galatasaray and neighbours Manchester City.
And while Mourinho saw glimpses of encouragement he expects a lot more finesse as he continues his work with the squad.
"I'm happy with some principles of our play - offensively and defensively - that we worked on in training," he explained.
"I could see them there, but not in a perfect way because conditions is not the best...10 days of training sessions, accumulation of fatigue, no sharpness.
"This takes time but I could see different things; they started thinking football the way I think and that pleased me.
"Everybody played, everybody had a positive performance, so I'm happy."
Source: PA