Former United boss Ole Gunnar Solskjaer and Michael Carrick, a decorated ex-United midfielder, have both been linked with the temporary role.
But regardless of United’s past pedigree, the chaos enveloping Old Trafford hardly makes it an appealing job for any manager of stature these days.
Welbeck, 35, was at United when they won their most recent Premier League title in 2013 under Alex Ferguson, who watched the Brighton debacle from the directors box as the current generation showed how far they have fallen from the Scot’s golden era.
United, currently a disappointing seventh in the Premier League, are without a win in four games and have managed only one victory in their last seven matches.
That wretched form is unlikely to improve any time soon with United hosting Manchester City next weekend before travelling to Premier League leaders Arsenal on January 25.
After a humiliating League Cup loss at fourth-tier Grimsby in August, United have exited both domestic cups at the first hurdle for the first time since 1981-82.
Avenging their 2023 FA Cup semifinal loss to United, Brighton have now won on four of their past five visits to Old Trafford.
United in disarray
United midfielder Kobbie Mainoo started for only the second time this season as Fletcher left Casemiro on the bench in one of three changes from the midweek 2-2 draw at lowly Burnley.
Albion keeper Jason Steele made fine saves to deny Diogo Dalot and Bruno Fernandes in the early stages.
But Brighton made the most of those escapes to take the lead in the 12th minute.
Welbeck was the catalyst with an incisive run and cross to Georginio Rutter, whose header was cleared off the line by Lisandro Martinez before Gruda slammed past Senne Lammens from close range.
United were in disarray and chants against co-owners Jim Ratcliffe and the Glazer family rang around Old Trafford.
Fernandes sent a free kick wide and Matheus Cunha was narrowly off-target as United trudged off with boos ringing in their ears at halftime.
Mainoo was hauled off in the second half after a lacklustre display that did little to rebuke Amorim’s decision to ignore him for much of this season.
United’s problems are far wider than just Mainoo and Brighton punished their shambolic defending to double the lead in the 64th minute.
Gruda was given time and space to pick out Welbeck inside the area and he lashed an exquisite strike past Lammens as the atmosphere turned even more toxic.
Sesko set up a frenetic finale after heading home from Fernandes’ 85th minute corner.
But United couldn’t muster a late escape as Lacey, already on a booking, brought a fitting end to a painful defeat when he was sent off for throwing the ball away in frustration.
-Agence France-Presse