Feyenoord 1 Manchester United 0
Hopes were high as Manchester United returned to the scene of Sir Alex Ferguson's first European triumph as United's manager. It was at the De Kuip stadium that the Red Devils enjoyed a glorious victory by defeating Barcelona 2-1 to lift the old European Cup Winners Cup back in 1991.
Their attention was now fully focused on the Europa League and a tricky opening group match against Dutch side Feyenoord, which would be the shortest trip for Mourinho's men in a group that will see them face longer journeys to Turkey and The Ukraine.
United departed Manchester with a squad that didn't include rested captain Rooney and injured Shaw but still had a side capable of seeing off the threat of the Dutch team.
Only three players started the game from the eleven that played in the derby so there was a chance for Smalling to partner Bailly in place of Blind and defensive duo Rojo and Darmian replaced Valencia and Shaw.
In midfield, Pogba remained but he had a new partner in Schneiderlin with Herrera and Mata in support.
Up front, the impressive Rashford was handed his first start of the season alongside Martial.
The opening ten minutes was a cagey affair with both sides weighing each other up until the home side tested De Gea with a curling shot from the edge of the area by Berghuis. The United number one was alert to the early threat.
A surging run from Herrera was halted by a foul which Pogba took but his effort on goal was easily saved by keeper Brad Jones.
United's first real chance fell to Martial in the 24th minute following good work from Darmian on the right side of the penalty area. His cross was low and hard and as it fell to Martial you felt it was goal-bound until it flew inches past the post.
The bright spark in the United side was the recalled Ander Herrera, who was covering every blade of grass on the pitch as he helped both the attack and defence.
Feyenoord had a slightly aggressive style to their play, which was shown in the number of free kicks they conceded as they tried to bully United out of their rhythm.
As the home side saw more of the ball the home supporters raised the atmosphere as they sensed their team were in the ascendancy this, in turn, prompted Mourinho to urge his players to calm down as he watched from the touchline.
As the half entered its final ten minutes it has to be said that United's play had been passive with no real threat in attack.
Mata almost got onto the end of a headed flick-on but that was as close it got as the half ended in a boring goalless draw.
Rashford cut a lone figure up front as he lacked any decent service and when he did gain possession he gave it away far too easily. The more he plays the quicker he will improve his all round game as his potential is immense.
At the start of the second half, Pogba slotted in higher up the pitch clearly looking to become more involved in the play than he was in the first forty-five minutes.
By the 55th minute the pace of the game hadn't picked up and it badly needed an infusion of energy from somewhere as Ibrahimovic started to warm up down on the touchline.
Pogba once again tried his luck from distance but his shot was wide of the mark.
After the hour mark, Mourinho had seen enough and made a triple substitution by bringing on Ibrahimovic, Memphis and Young in place of Rashford, Martial and Mata.
As the match entered its final fifteen minutes it was a match even in chances, but with United edging the amount of possession without managing to create any clear-cut openings.
Ibrahimovic did manage to rise the highest to another Young delivery from a free kick, but the big Swede directed his header too high.
Then Feyenoord took the lead on the counter with a goal that should have been ruled out for offside during the build up. Jorgensen was allowed to play on and crossed from the right and found an unmarked Vilhena in the box to fire easily past De Gea.
It was shocking defensive play by United who seemed to stop for the offside flag that never came and ended up conceding a sloppy goal.
To their credit United did go on the attack immediately after conceding and it was Smalling who almost benefitted from a neat flick from Ibrahimovic but his shot was blocked by a crowd of defenders.
As the clock hit 90 minutes Ibrahimovic took over the free kick duties and fired a thirty yard effort hard and goal bound that the keeper did well to get his body behind.
It was then the turn of Herrera, who was just about to pull the trigger until a late tackle on him denied him the chance of grabbing an equaliser. That was the last piece of action on a night that will not linger in the memory as there was absolutely nothing memorable in United's play whatsoever.
An opening defeat in the group stage isn't a disaster. However, there are tougher matches ahead and if United do in fact want to add this trophy to their museum showcase then Mourinho will have to put a bomb under his players.
Mata and Herrera huffed and puffed without creating anything of substance. Pogba has yet to hit his stride and he played with a new midfield partner in Schneiderlin who did his job well enough after a spell on the sidelines.
Up front Martial has yet to hit the heights of last season and you would expect a player of his quality to hit top form soon. Rashford failed to live up to the hype surrounding his recent exploits, but he is young and will hopefully learn from the bad games as well as the good ones.
Two defeats on the bounce now and Mourinho will have to pick a side capable of beating Watford in the Premier League to avoid a hat-trick of defeats.
Until then thanks for reading.