The Red Devils poor first-half display was forgotten about in the second half, as they found the net twice to guide themselves to three hard-fought points.
United have now won 95 Premier League matches after conceding the first goal - seven more comebacks than any other team in Premier League history.
VAVEL UK looks back on the talking points of United's victory.
11 points clear of 5th
Ole Gunnar Solskjaer's Reds entertained Brighton on Sunday evening knowing their top-four rivals in Chelsea, Spurs and Leicester all failed to collect three points in their respective fixtures.
The pressure was on the Reds to capitalise on the mistakes of their rivals, their win over Brighton solidifies their position in the top four. Solskjaer's side is now 11 points clear of 5th place Spurs - who they visit in next week's league game.
With a Europa League quarter-final to play against Granada and a visit to Spurs in the next seven days, Solskjaer could opt to play a stronger team in Spain and afford to make team changes at Tottenham - due to his sides comfortable top-four position.
Greenwood excels in the 9 role
With the unfortunate news of Anthony Martial's injury ruling him out for the rest of the season, Edinson Cavani was called back into the side to replace the Frenchman at strike.
The Uruguayan's under-par performance resulted in Solskjaer substituting the veteran to replace him with Donny Van de Beek.
That important substitution allowed Greenwood to move from the right-wing to feature to his preferred role at strike for the final seven minutes of the game.
And only a minute later after the substitution, the 19-year-old headed home from inside the six-yard box, in true fox in the box fashion to win the game.
With Cavani's poor form, Rashford's injury issues and Martial's potentially out for the season, next week's Europa League clash against Granada could give Greenwood the chance to stake a claim as United's number nine.
Greenwood post-match comments signified how he is slowly getting back into gear after a tough season.
“Yeah, I’m getting back into the zone," Greenwood told MUTV.
“It’s somewhere I wanted to be earlier in the season but it’s come now. I’ve kept my head down and just concentrated, worked in training and I’m happy it’s coming on to the pitch now.”
Regarded as the best finisher at the club by Solskjaer, Greenwood may have the heavy task of leading United's line in their quest for silverware - having not won a trophy since 2017.