Graham Potter's side played some flamboyant football throughout the 90 minutes, but particularly for the first hour or so, when they had the visitors pinned in their own half for multiple spells.
The Red Devils looked underconfident and had problems stringing passes on a day when their midfield looked inferior to the opposition's. Manchester United had Scott McTominay and Nemanja Matic in midfield, behind Juan Mata, who played in a No.10 role.
Although the Serbian was substituted at half-time for Edinson Cavani, the Scottish international continued. However, his performance was below average as he gave away unnecessary fouls in dangerous areas on the pitch and failed to read the movement of his opponents.
McTominay was poor when he was required to drop back and shield his backline and was majorly ineffective in helping his team hold on to the ball. In fact, Fred, who came on the pitch at half-time, was more impressive than McTominay despite playing only one half. Twitter did not hold back in slamming the 25-year old for his wasteful display.
Manchester United's hope of a top-four finish are dead mathematically as they hit another low
If the Red Devils had managed to win all three points at the Amex, they still had an outside chance of securing Champions League football. It would have taken some poor performances from rivals Tottenham Hotspur and Arsenal, but the possibility was still alive.
However, after their embarrassing 4-0 defeat, it has been confirmed that there will definitely be no Champions League football for Manchester United. But the Old Trafford outfit have also hit another low after this loss. They only have one game remaining in the campaign, which means that a win from their last game will leave them with a points tally of 61.
This will be United's lowest total in the history of the Premier League, with the previous lowest being 64 points in the 2013-14 campaign. With the four goals they conceded today, Manchester United ensured that this will go down as their worst season defensively as well, having conceded 56 throughout the season.
It could get worse with that one game remaining against Crystal Palace. Erik ten Hag must be losing sleep after witnessing such a dreadful performance from his future side.