Despite the occasion, this was a match that mattered little to a United team that had already won their group but both teams contributed to a relatively end-to-end and high-octane affair in blisteringly cold weather conditions.
Mason Greenwood opened the scoring in stunning fashion before Rieder equalised with an equally brilliant finish.
Story of the match
Rangnick made eleven changes to the team that won against Crystal Palace – young, old, and others on the fringes with a point to prove.
In the opening minutes, experience linked up with exuberance as Mata's clipped pass over the Young Boys defence found Amad Diallo, but the 19-year-old Ivorian's shot was weak and Guillaume Faivre easily saved.
However, on nine minutes, the link between young and old produced very different results.
Perhaps it is a bit harsh to call Luke Shaw old, however, he does seem to have been around the block for a while – even at 26! The left-back took his time to fire a cross into the box and the predatory Greenwood finished it off with a sublime scissor-kick into the bottom corner. It was a strike that will have left his manager very impressed.
Dean Henderson had been relatively untroubled from a saves perspective but he was called into action just before the half-hour mark, keeping hold of a fierce 30-yard effort from Michel Aebisher.
Shortly after this action, chants in support of former manager Ole Gunnar Solskjaer started to ring around the Stretford End. Despite a difficult end to his career as United manager, the Norwegian will always be a legend in these parts.
Amad had another great chance to get himself on the scoresheet after being played in by Jesse Lingard but he dithered and delayed, before loosing possession.
At the other end, Young Boys broke and Jordan Pefok stung the gloves of Henderson with a snap-shot inside the box.
Shortly after, Greenwood did incredibly well to surge down the bi-line and roll the ball across to an unmarked Mata. The Spaniard looked destined to make it 2-0 but a combination of Fabian Lustenberger and Faivre managed to deflect the ball over the bar.
United's profligacy in front of goal was made to pay just before half-time and, in fairness, it was a beautiful finish from Rieder.
Donny van de Beek sloppily lost the ball, just outside the box, and the winger seized upon the loose ball before curling an outrageous 25-yard strike into the top corner. You could say that was Rieder out of the top drawer!
United started the second-half with a vengeance and Lingard again turned provider for Amad but, again, the youngster couldn't quite get the purchase on his shot.
The game then settled down after that quick start to the second period but it was United carved open the next big chance - and what a chance it was for Anthony Elanga.
Lingard, involved in a lot for United on the night, threaded the youngster in on goal but Faivre stayed tall to make the block with his body.
Rangnick replaced Shaw on the hour with another academy prospect, Teden Menghi, a further illustration of the exhibition feel that this game had.
Sivan Hefti came off the bench as part of a triple change by Wagner and he nearly made an instant impression, knocking a looped ball back across for Quentin Maceiras, but the advanced right-back's rasping effort fizzed narrowly wide of Henderson's post.
Charlie Savage and Zidane Iqbal also came on for late cameos. The United academy wheel was in full swing!
Invariably, as the game wore on, rain started to get heavier and both teams started to get a little bit sloppier. With nothing on the line, though, spectators should have been grateful for the relatively entertaining match that they got for the most part.