Ruben Amorim's side are languishing in 15th place following the latest setback in their wretched top-flight campaign.

United are focused on salvaging their forgettable season by winning the Europa League.

They will host Athletic Bilbao in the semi-final second leg next Thursday protecting a 3-0 lead and Amorim made a host of changes, resting Harry Maguire, Bruno Fernandes and Casemiro.

With an average age of 22 years and 270 days, United's starting line-up was the third-youngest in Premier League history.

Aged 17 years and 156 days, Chido Obi became the youngest player to start a Premier League match for United, while inexperienced duo Tyler Fredricson and Harry Amass also featured.

In the 14th minute, Mason Mount scored only his second league goal for United since joining from Chelsea in 2023 as he took Alejandro Garnacho's pass and slotted home from eight yards.

But Brentford hit back in the 27th minute when United defender Luke Shaw deflected Michael Kayode's effort into his own net.

United's leaky defence were punished in the 33rd minute as Kevin Schade headed Christian Norgaard's cross past Altay Bayindir.

Adding to Amorim's problems, United defender Matthijs de Ligt limped off with a first half injury.

Lacklustre United conceded again when Schade struck with a 70th minute header.

Yoane Wissa completed the rout four minutes later, poking home for his 18th league goal this season.

Garnacho's 82nd minute blast from the edge of the area was followed by Amad Diallo's stoppage-time effort for the visitors.

But it was little consolation for United, who have lost 12 of Amorim's 24 league games, winning only six times.