After a frustrating 90 minutes on the clock, the game entered stoppage time with United bombing forward with all their might. Luke Shaw's long ball from halfway line found Romelu Lukaku whose flick-on header found his fellow Belgian, who found the bottom corner of the net ending the away side's run in Europe this season.
The goal meant that the home side did not make an unwanted record of going three straight European matches at home without a goal.
Fellaini's goal masked an otherwise unimpressive display from the English giants who were wasteful on a lot of occasions in the first half. Jose Mourinho made six changes to the starting XI from the draw against Crystal Palace. Marcus Rashford was picked to start over Lukaku and missed several chances despite being lively throughout the match.
It was an incredible night of Champions League football as it saw seven teams, many of them struggling in domestic leagues, qualify for the next round.
#1 More shots, more goals
Jose Mourinho's men had 21 shots in total compared to Young Boys' 11 shots. A front three of Rashford, Jesse Lingard and the in-form Anthony Martial had a majority of these chances but failed to convert them into goals.
Rashford was lively from the first minute and proved to be a handful for the Swiss side's defense. Once again though, Rashford missed a chance to overthrow Lukaku as Mourinho's preferred No.9 as the Englishman missed a lot of opportunities to score. In the 5th minute, he was one-on-one with the keeper and tried to chip him only to see his attempt sail well over the crossbar.
Most of Martial's shots were blocked by the opposition defense or went off target. All the pressure from the home side finally counted when the Belgian midfielder netted once more late in the second half to get all three points.