Amad was introduced at half-time following a nervy 45 minutes for United, with Milan seeing two goals ruled out by the officials for offside (Rafael Leao) and handball (Franck Kessie) respectively.
And 18-year-old Amad immediately repaid Solskjaer’s faith with an impudent ‘backward’ header reminiscent of a Javier Hernandez goal against Stoke back in 2010 that remains famous among United fans.
The Ivory Coast teenager made a darting run through Milan’s defence five minutes into the second half and was found with a fine ball over the top by Bruno Fernandes.
Amad still had a lot to do but fooled Milan goalkeeper Gianluigi Donnarumma by looping a header into the net with his back to goal to announce himself to United fans.
However, United fell deeper and deeper as the game wore on, and Simon Kjaer’s injury-time header sealed a vital away goal for Milan to take into the second leg.