The fanfare of the record-breaking return of Mr Champions League, Cristiano Ronaldo in the colors of Manchester United in the most prestigious club football competition was overshadowed by a poor outing from the Reds in Switzerland against Young Boys as they fell 2-1.
Cristiano Ronaldo was making his 177th Champions League appearance, equalling the all-time record held by former Spain and Real Madrid goalkeeper, Iker Casillas.
The host were first to fire the warning shot, a clear sign to their visitors not to underestimate their power. Meschak Elia cut in on the edge of the 18-yard box as early as the third minute, after beating Fred, but his shot failed to hit the target.
United responded in the 13th minute with the first goal of the night and from the usual culprit, Cristiano Ronaldo. A silk cross from his compatriot, Bruno Fernandes with the outside of his right foot from the left was powered home by Ronaldo beyond Von Ballmos in goal.
Young Boys also got their own chance at the other end. Christian Fassnacht was denied by David de Gea, before Ronaldo saw his other effort parried for a corner by Von Ballmos.
The game took a game-changing turn in the 35th minute when Aaron Wan Bissaka was shown his matching orders for stamping on Martins' foot after losing the ball. Jadon Sancho was sacrificed for the introduction of Diogo Dalot afterwards.
Fassnacht should have equalized with seven minutes of the first half left, but his effort was wide off goal from a ball across the face of goal. That was a goal that could have changed the game instantly.
There were cries for a penalty on the 53rd minute from Ronaldo after he felt he was fouled by Mohammed Ali Camara who put pressure on him, after he had received a ball through on goal from Fernandes. The referee wasted no time in dismissing his shouts.
The hosts eventually leveled things up in the 65th minute as a low cross from Silvan Hefti was met by. A toe-poking effort Moumi Ngamaleu at the far post. The Cameroonian almost doubled his tally moments later, be he couldn't manage his effort from the left side of the box on target.
Eyebrows were raised in the 72nd minute when Ole Gunnar Solskjaer substituted, arguable two of his most influential players in the squad, Fernandes and Ronaldo for Nemanja Matic and Jesse Lingard, a decision that would eventually cost United three points.
Sandro Lapteu almost condemned United to defeat with three minutes of regulation time to play, when his dipping effort from range was heading for under the crossbar. De Gea had to be on his toes to tip the ball over.
The decision by Solskjaer to replace Ronaldo with Lingard eventually backfired as the England international, who is on his way to redeeming his career at United, handed the hosts the win in the last minute of additional time.
An ill-timed back-pass from Lingard was well into the path of American youngster, Theoson Siabetchu, who cooly slotted beyond De Gea from the middle of the box to hand the Swiss club a famous victory.
It was a remarkable victory for Young Boys, especially over Manchester United, against whom they have lost in their last two meetings.
A massive three points to start their European campaign and positives to execute their remaining group games, remembering that they finish last in their group in 2019, their last time out in the competition.
Questions were raised about Solskjaer's decision to take off Ronaldo and Fernandes at the same time, with many questioning his tactics.
United will need to pick themselves up and up their games against more tactical sides like Villarreal, to whom they lost last season's Europa League final and Atalanta in their next group matches.