The fact that debutant Axel Tuanzebe was United's best player - apart from possibly Anthony Martial - said everything about the team's performance at Arsenal.
It was a largely ineffective and apathetic showing from a side with a clear focus on the looming semi final with Celta Vigo.
There were eight changes from the first leg team in Spain, and Chris Smalling and Phil Jones were made to look like the debutant rookies on their returns from injury.
Tuanzebe showed far more composure, bravery and intelligence than both of his senior centre halves and looks set for a very bright Old Trafford future.
Ander Herrera has had the best season of his United career but was at fault for the Arsenal opener, turning his back on the ball instead of closing down Granit Xhaka.
Chris Smalling was left exposed and out of position for Danny Welbeck's header and Jones was cumbersome and awkward.
Juan Mata started brightly but understandably faded on his first start for two months, with Paul Pogba and Marcus Rashford on the bench.
With Antonio Valencia rested, Ashley Young and Tim Fosu - Mensah injured and Matteo Darmian on the left, a dearth of right-backs resulted in 19-year-old Tuanzebe's call up.
A centre-half by trade, his senior bow came in the 68th minute of United's routine 4-0 win over Wigan in the FA Cup fourth round.
His full debut came in a vastly different environment and with a much more difficult assignment - the task of shackling Arsenal's main man and one of the best in the world, Alexis Sanchez.
Captain of the Under 23 side at only 19, and up against the Chilean in an unfamiliar position, Tuanzebe showed why his full debut was one that's long overdue.
His impressive and diligent performance was the only positive on an otherwise instantly forgettable day for the team.
Even the most seasoned Premier League player has been roasted by Sanchez, but, far from being overawed, Tuanzebe held his own at right-back.
Jose has made no secret of his desire to prioritise the Europa League and will rest several of his senior alumni for the league run in.
Having made a mockery of his perceived reluctance to put faith in youth, more chances look set to follow for the squad's young fringe players in the coming weeks.
Tuanzebe's performance at Arsenal contrasted starkly with those of Smalling and Jones and - with three league games left- he's surely at the front of the line.