After Juan Mata was the one to replace Mason Greenwood before extra time began, Ighalo returned to his seat in the stands looking a little downbeat and Ole Gunnar Solskjaer, no doubt drawing on his own experiences as a player, felt the need to offer guidance.
Greek worldwide Zeca, clearly a United enthusiast, has been with Copenhagen since 2017 and previously made 249 appearances for Panathinaikos in a six-year spell.
It broke a fearless resistance from the Danish champions, who had defended brilliantly but did ride their luck slightly as Mason Greenwood and Fernandes both had struck the post in normal time and Greenwood had a goal ruled out by VAR in the first half for offside.
Former Everton full-back Bryan Oviedo was thwarted by a brilliant block from Aaron Wan-Bissaka, who made up for his wasteful performance in the final third with a quality piece of defending. At this stage of this season it is important to win games like today and we go through. "He was giving you the ball all the time".
Martial almost won the game in normal time but again a sprawling Johnsson tipped away his curling attempt that appeared destined for the top corner.
But for Zeca, Copenhagen's elimination from Europe comes with a silver lining - he gets to see his boyhood club take part in their first European semi-final since Jose Mourinho took United to the Europa League crown in 2017.
Inter struck first as Nicolo Barella guided in from the edge of the area on 15 minutes, with Lukaku bundling in a second six minutes later.
German midfielder Kai Havertz narrowed the gap for Bayer Leverkusen, but Inter secured the victory. His 13 saves against United was the most in one Europa League game since 2009. "We will have to be ready".