Bruno Fernandes' extra-time penalty edged Manchester United through to the Europa League semi-finals as Ole Gunnar Solskjaer's side toiled to victory against gutsy FC Copenhagen.
An overturned penalty, two disallowed goals and efforts off the woodwork frustrated the Old Trafford giants during a goalless 90 minutes in which the Danish side looked dangerous despite failing to register a shot on target.
Fernandes would save the day from the spot in extra time, securing a 1-0 victory and a last-four date against Wolves or Sevilla back at Stadion Koln this Sunday.
Solskjaer will need a vastly-improved performance if they are to get any further than that, though, as their tired, sloppy play was compounded by Copenhagen playing with the intensity you would expect from a side in their first European quarter-final.
Ole Gunnar Solskjaer's side improved after a poor opening 45 minutes and dominated the second half but could find no way past inspired goalkeeper Karl-Johan Johnsson.
The match was on a knife-edge as play headed into extra time, which was just five minutes old when Fernandes scored from a spot-kick won by Anthony Martial.
United midfielder Juan Mata, who made a huge difference when he came on for extra-time, said: "The team is quite tired physically. At this stage of this season it is important to win games like today and we go through. We stay in Germany for quite some time and hopefully we can win."