Manchester United's problems mounted as they crashed out of the League Cup after blowing a two-goal lead in a stunning 3-2 defeat against Brighton on Wednesday.
Michael Carrick's side slumped to their second successive home defeat following a wretched collapse in the third round at Old Trafford.
United led through goals from Shea Lacey and Mason Mount inside just 10 minutes. But Charalampos Kostoulas sparked Brighton's revival and Pascal Gross equalised before Maxim De Cuyper grabbed the winner to leave Carrick shell-shocked as his team were booed off.
It was another brutal blow for United after their controversial 1-0 home defeat against Manchester City on Sunday.
The referees' governing body admitted that VAR officials were wrong to allow City striker Erling Haaland's winner, which left United with only one win from their first four Premier League matches.
Having led United to third place last season in his spell as interim boss, Carrick was expected to oversee a title challenge this term after being appointed on a permanent basis. But United have already lost three times in six games in all competitions, putting Carrick under pressure to turn the tide at Fulham in the top-flight on Sunday.
A defeat in west London at the weekend would leave United in a full-blown crisis barely a month into the new campaign.
Amid criticism of United's close-season transfer recruitment, Carrick's decision to make eight changes exposed the lack of depth in his squad.
At least Lacey offers hope for the future at United, unlike fellow highly rated teenager JJ Gabriel, who has reportedly expressed his wish to leave Old Trafford.
The 19-year-old midfielder showed why Carrick has put his faith in him after eight minutes.
Taking possession just inside the Brighton penalty area, Lacey bagged his first ever goal for United as he lashed a clinical finish into the bottom corner.
Mount doubled United's lead two minutes later, pouncing to fire into the roof of the net after Marcus Rashford's shot was saved by Jason Steele. But United's defensive issues resurfaced in first-half stoppage time when Kostoulas punished poor marking from Ayden Heaven to drill past Karl Darlow.
SLOPPY UNITED
That setback unnerved United and they conceded a 65th-minute equaliser as Gross controlled Luka Vuskovic's header and fired home from close range.
Carrick's men were in disarray and Brighton struck again in the 70th minute when De Cuyper swept Kostoulas's pass into the net from six yards after sloppy United defending.
Carrick sent on Bruno Fernandes and Matheus Cunha in the closing stages but United were unable to find an equaliser.
Brighton have now knocked United out of two cups in the space of nine months after winning in the FA Cup at Old Trafford in January.
It was the first time in 50 years that United had lost after being 2-0 up at home.
ABRAHAM STARS FOR VILLA
Tammy Abraham starred as Aston Villa won for just the second time this season, beating Coventry 3-1 at the CBS Arena.
Villa and Coventry are both in the Premier League relegation zone after dismal starts to the season.
Unai Emery's men, beaten three times in four league games, showed signs of stopping the rot as Abraham slotted home from George Hemmings's deft pass in the seventh minute.
Victor Torp hauled Coventry level with a superb free-kick in the 27th minute.
Ross Barkley restored Villa's lead five minutes before half-time with a header from Ibrahim Mbaye's corner.
Abraham killed off Coventry when he slotted home from Barkley's flick in the 59th minute.
Charly Alcaraz came off the bench to seal Everton's 1-0 win over second tier Wolves with a curling
strike in the 80th minute.
Fourth tier Fleetwood Town reached the fourth round for the first time, beating Championship side Sheffield United 1-0.
On Tuesday, Arsenal won 4-2 at Ipswich, Liverpool beat troubled Tottenham 3-1, Fulham claimed a
3-2 win at West Ham and Brentford won 2-1 at Reading.
Holders Manchester City host Norwich on Thursday.