Brazilian forward Antony stepped off the bench to send Manchester United through to the Europa League last 16, with the hosts coming from behind to beat Barcelona 2-1 in Thursday's playoff second leg, progressing 4-3 on aggregate.
After a frantic start, Barca were awarded a 18th minute penalty, much to United's frustration, after Bruno Fernandes was adjudged to have fouled defender Alejandro Balde, with Robert Lewandowski just squeezing the resulting spot kick home.
United came out for the second half looking like a different side and levelled through Fred, the Brazilian steering home Fernandes' pass two minutes after the break.