Looking to avenge their 4-2 Premier League defeat at the Theatre of Dreams in October, Brighton raced into a one-goal lead after midfielder Brajan Gruda found the back of the net after just 12 minutes.
And the Seagulls, unbeaten in their previous three games beforehand, were two goals to the good when Gruda turned provider for Welbeck, who unleashed a fierce left-footed strike just after the hour mark. The 35-year-old made 142 appearances for United after emerging through the club’s youth system in 2008.
United threatened a dramatic fightback when Benjamin Sesko, who scored both goals in Wednesday’s 2-2 league draw with Burnley, was on target once again with just five minutes of normal time left to play.
But all hope was soon lost when youngster Lacey, a bright spark in recent outings against Burnley and Aston Villa, received a second yellow card after bouncing the ball in frustration following a decision which went against him.
The 18-year-old - who was full of emotion after emerging from the substitutes bench - had previously been cautioned for a late tackle.
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