The Red Devils fell to their first loss of the Premier League season late on against the Seagulls in a leaky Amex Stadium.
Danny Welbeck netted his 100th career goal before Amad Diallo equalised for the visitors.
Man United were further frustrated after Joshua Zirkzee’s offside saw a potential winning goal ruled out.
To make matters even worse, Erik ten Hag’s side failed to hold on to a draw as Joao Pedro headed in a later winner.
Manchester United legend Gary Neville has pointed the finger at Casemiro for Brighton’s late winner in Saturday’s defeat.
“I think particularly if you watch Casemiro, it looks to me, I’ve only watched it once back on the replay, it looks like he leaves his position at that back post and runs back towards central midfield,” he said.
“But then it leaves an acre of space in that back zone where three Brighton players are queuing up. Lack of concentration, lack of focus and it does put some pressure on them.”
Neville’s comments suggest that Casemiro’s error was a crucial factor in the goal and that his lack of focus put pressure on the rest of the team.
