Brentford 3-1 Man United: Ruben Amorim's malfunctioning side are punished for Sunday League-style failings as Igor Thiago stars with superb double for brave and ambitious Bees

Manchester United's misery rolls on and before long its momentum will drown yet another manager. Ruben Amorim is not improving this malfunctioning set of footballers and it's only a matter of time before the ice breaks beneath his feet.

Amorim's first anniversary looms and the numbers are damning. The Portuguese has amassed 34 points from his 33 games in charge in the Premier League. In the old days, they called that relegation form.

Here, as brave and energetic and ambitious Brentford turned them over, they were as fallible as they often are. New players, same mistakes.

Much is made of Amorim's formation and way of playing and it's a valid argument. He is inflexible to the point of self-harm.

But the truth is that his players continue to exhibit basic failings. They don't have positional discipline, they don't track runners when teams break on them and they don't do the Sunday League stuff either - winning headers and timing tackles.

We have been watching this for years, not only on Amorim's watch. But these are coaching failings that land at Amorim's door and on a frantic afternoon in West London they undid his team once again.

This, largely, was a game that was decided in an opening 20 minute period that saw Brentford score twice through their energetic forward Igor Thiago. The first was a stormer, the second the work of a pickpocket.

United were dizzy and although Brentford goalkeeper Caoimihn Kelleher offered them a way back - and a first United goal to Benjamin Sesko - with a mistake in the 26th minute - he was to redeem himself when he saved a Bruno Fernandes penalty with 15 minutes left.

Brentford sealed the game in added time as Mathias Jensen broke and scored with venom and another United afternoon had ended in a return to a basic question. What will it take to make this team better?

United have struggled in this part of London before and they are not alone. Brentford – under Thomas Frank and now Keith Andrews – will run all over you with energy and ambition if you aren’t on your mettle.

And United weren’t. Indeed, it’s worth asking if they have any mettle under Amorim. If they do, it needs some polish.

Here they were as ragged and seemingly unprepared and unaware for the first half an hour as they have ever been on Amorim’s uncertain watch. Watching them buckle under Brentford’s direct football and rapid counters, it was tempting to wonder if they had done any preparation.

The home team were two goals up within 20 minutes and at that stage the United goalkeeper Altay Bayindir had been the visitors’ best player. That said everything.

In the eight minute, however, Bayindir had been as helpless as everybody else. Jordan Henderson picked up a loose ball ten yards outside his own penalty area and drilled a long pass over the United back four.

Harry Maguire probably could have headed it. But he didn’t. Instead he stepped up in a bid to play Thiago offside only to make a mess of it. The Brentford forward was the right side of the margins and ran through to belt a rising drive high to Bayindir’s right and in to the roof of the net. What a finish.

Brentford sensed United vulnerability. We all did. Pretty soon Bayindir made two good saves from headers from Sepp ven den Berg and Nathan Collins and at that stage they seemed as though they may keep his team in the game.

It wasn’t long, however, before Matthijs de Ligt chose not to head a pass down the left channel away and when Thiago fed Kevin Schade, he made sure he was in the middle to slide in his second goal after Bayindir had pawed away the cross.

Brentford were enjoying themselves while United fell foul of familiar basic flaws.

United were not without a threat of their own. Matheus Cunha was back from injury and that helped. One low shot – with the score at 1-0 – was kept out well by Keleher.

That said, Kelleher did have his fingerprints – or not as the case may be – all over the goal that gave United an undeserved lifeline in the 26th minute.

Patrick Dorgu’s looped cross from the left byline was hopeful and Kelleher – once of Liverpool – should have made it his own or left it alone. Ultimately his punch was weak and Sesko was able to benefit from the chaos that followed to score from six yards. Brentford appealed for a foul on their goalkeeper and VAR had a look but should not have. There was nothing to see.

United were better than point on. They were far from where and what they need to be but they were less ragged and more organised. They played with more control and a little higher up the field.

Still, the better chances between then and United’s missed penalty in the 75th minute belonged to Brentford.

For Andrews’ team, Henderson was excellent at the base of their midfield. Thus far, he looks a good summer buy. Down the left, meanwhile, Schade was far too good for Diogo Dalot, bullying the United wing-back routinely.

Twice Bayindir saved importantly. The first was routine as Van den Berg could only apply soft contact to a headed knock down. The second was excellent, Bayindir diving left to parry a low shot from Dango Ouattara after Schade had done his thing and provided then pull-back.

As it meandered in to its final stages, the game was in the balance. United carried a threat even if they weren’t creating chances. And then came the penalty. Cunha crossed from the right and as Mbuemo looked to profit, Collins pulled him down. Collins could have walked for his sins but VAR decided – questionably – that a yellow card was sufficient. Fernandes – after an age – took the penalty low and left and Kelleher plunged to save well.

That was the fourth penalty out of seven faced in his career – excluding shoot-outs – that the Brentford goalkeeper had saved. As the game reached the eight added minutes, it was responsible for a game on a knife edge.

United had enough time, that was for sure. But they didn't use it. Substitute Joshua Zirkzee placed one header over the bar but that was as good as it got before one final attack broke down and Brentford broke away for Jensen to smash the decisive goal past Bayindir from the edge of the penalty area.