Cristiano Ronaldo scored again for Manchester United, but they were beaten 2-1 late on by Young Boys in their Champions League opener after Aaron Wan-Bissaka's red card
Despite playing with 10 men 55 minutes, it looked like a solid defensive display would see United come away with a point
But a late error from Jesse Lingard allowed Jordan Pefok (90+5) to slot home the winner with the final kick of the game
Man Utd had been heavy favourites heading into the game, and made the perfect start as Ronaldo - who went level with Iker Casillas on all-time Champions League appearances (177) - slotted through David Von Ballmoos' legs inside 13 minutes
But the complexion of the match-up was changed in the 35th minute as Wan-Bissaka was shown a straight red for a heavy and clumsy challenge on Christopher Martins
Sensing an opportunity and buoyed by a passionate home crowd, Young Boys pressed and probed for the leveller and made the breakthrough midway through the second half
 Moumi Ngamaleu (66) poked the ball past David de Gea, before Pefok scored a late second following continuous pressure from the hosts
It was a nightmare start for Man Utd in Group F, who will welcome Villarreal - who beat them in the Europa League final three months ago - to Old Trafford in two weeks' time in desperate need of three points
Both sides had sights of goal in the opening four minutes
 Meschak Elia muscled Fred out of the way to pick up a loose Jadon Sancho pass, but driving into the box
 However, his effort bobbled wide of the target
 At the other end, Bruno Fernandes dinked a wonderful ball in from the left, trying to pick out Sancho's run, but goalkeeper Von Ballmoos easily collected
But soon after, the Young Boys stopper would have been disappointed in the manner he conceded the opener from Ronaldo
 Fernandes lifted in a superb pass, picking out the run of Ronaldo at the back, who slotted the ball through Von Ballmoos' legs as it trickled over the line
Both goalkeepers were called into action just before the half-hour mark
 Christian Fassnacht cut to the top of the area from the right, but his strike stung the palms of David De Gea
 Man Utd then broke at the other end, Fernandes feeding Ronaldo again, but the latter's strike was saved well by the Young Boys goalkeeper
But in the 35th minute, the tide turned for Man Utd as Wan-Bissaka was shown a straight red card
 It was a careless, studs-up challenge on Martins, and the referee rightly produced the red card
 Soon after, Young Boys had their best chance of the game
 Ulisses Garcia's cross flashed through the area, with Fassnecht driving onto it over on the right
 However, his fierce volley dragged just inches wide of the far post
With Young Boys pushing for the equaliser, United need to regroup at half-time and introduced Raphael Varane for the second half
 Ronaldo cut a solitary figure up-front as the waves of Young Boys attacks kept coming, but had a penalty shout in the 53rd minute, going down in the area with Mohamed Camara at his shoulder
 However, the referee emphatically waved away the claims
Young Boys made a deserved breakthrough in the 66th minute
 The impressive Elia sent an inviting cross in from the right, with Ngamaleu poking a foot in front of Varane and flicking the ball past De Gea at the near post, with the ultra fans behind the goal erupting into jubilant scenes of celebration
The hosts continued to press for a winner - Sandro Lauper forced a fingertip save from De Gea - but it was a huge error from Lingard that Young Boys took advantage of
 A sloppy pass from the substitute left Pefok through on goal, and he easily slotted home past the United goalkeeper
He was mobbed by his teammates - substitutes included - as he wheeled away to celebrate in front of the packed-out home end, as United were left to reflect on a dismal evening in Bern
An impressive performance from the forward
 He had a superb early chance and easily beat Fred down the left not long after, proving to be a handful
 He provided a wonderful assist for the equaliser, and had been playing inviting crosses such as those in from the start
 Thankfully, it eventually paid off
 "We've won a couple of games already, but to beat Manchester United in the Champions League is unique
 I'm just really happy for everyone who witnessed it
 Every single person here played their part
"The lads went above and beyond their limits
 That's only possible with great support
 We wanted to show our intensity, our aggression and our passion
 The lads did brilliantly and deserve huge credit
""I thought we could have done better in the first half with 11 men, but we always knew they were high intensity, energetic, athletic team and I thought we started OK
 But we didn't get the second goal that would have killed the game off
 In the second half, we felt in control without the ball
 They didn't create any big chances, but there were two unfortunate goals
"I can understand why he gives it because Aaron takes a touch that goes too far
 It's never a dangerous tackle because it hits him on the front of his foot
 We've seen sometimes - a bit like Harvey Elliot - bad injuries and there was never reckless or malicious
"But probably a little bit inexperienced to go through without having the ball
 But it makes it difficult after that with ten men
"That's football for you at the highest level
 A lack of concentration, make a mistake and you get punished
 We did that last year in Europe, we conceded two very sloppy counter-attacks against Istanbul and we lost that game
"Today, the last seconds, Jesse wants to play it safe and misplaces a pass and we concede a goal
 It happens in football
 Harry Hindsight is a very good player so if Jesse could have that chance again, he'll turn and boot it the other way
 But we'll learn from it
"We know we've given ourselves a more difficult task than we did last year, but everyone thought we were through after two games last year
 You need ten, maybe 12 points, win all your home games and maybe one away from home
 We've lost an opportunity to get three points, but we've got two home games next and we'll focus on those two
""Manchester United haven't got going
 Against Wolves, they were very fortunate
 Against Newcastle when it was 1-1, it was a heads-or-tails game
 It could have easily gone Newcastle's way
"Champions League football is hard and it doesn't matter who you are playing
 For Young Boys, this is their biggest game ever
 And if you don't match that, you are in trouble