David de Gea produced a horrendous mistake to gift Brentford the opener in Manchester United's trip to west London on Saturday afternoon.

United were looking to bounce back from their miserable 2-1 defeat to Brighton in their opening game of the season last weekend.

Erik ten Hag made one change to his side from that defeat.

The legendary Cristiano Ronaldo was reinstalled to the starting line-up while Scott McTominay dropped to the bench.

But the change did not have the desired effect as United endured a disastrous first-half at the Gtech Community Stadium.

United fell behind inside 10 minutes after a howler of epic proportions from De Gea.

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Josh Dasilva drove forward and tried his luck from outside the box. His effort was tame and looked as if it would be easily gathered by De Gea.

But the Spaniard dived over the ball and let it squirm underneath him and into the net. Watch the mistake below...

What a poor error. It goes without saying that De Gea should have kept Dasilva's effort with ease.

Brentford took a 2-0 lead shortly after thanks to some more terrible defending from United.

Christian Eriksen was dispossessed by Mathias Jensen just inside United's box after being put under all sorts of pressure by De Gea.

Jensen then dispatched his effort past De Gea.

Ben Mee made it 3-0 on the half-hour mark after heading home from a corner. And, incredibly, it was 4-0 shortly after when Bryan Mbeumo found the back of the net after a lightning quick counter-attack.

It has been a truly disastrous start to the season for United. There was hope that Ten Hag could transform their fortunes after a dismal 2021/22 season. But the Red Devils have picked up exactly where they left off.

It's clear that United need reinforcements - and they need them fast.