Manchester United's 3-0 loss to Manchester City in Sunday's derby increased the pressure on head coach Ruben Amorim and raised more questions about his favoured 3-4-2-1 system.
Amorim reiterated his commitment to it despite the result. "I'm not going to change," he said. "When I want to change my philosophy, I will change. If not, you have to change the man."
It is understood the club remain patient and have no plans to change their head coach. But can Amorim's three-at-the-back set-up still bring success to Old Trafford, or is it doomed to fail?
Between the Lines returns with a look at his approach, a breakdown of how formations have evolved in the Premier League, and an examination of the system's issues at Manchester United.
Amorim's three-at-the-back faith
When Amorim says he won't change, history suggests he means it.
He has started with a back three in 189 consecutive league games as a head coach since his appointment as Sporting boss in 2020.
His most popular variation is 3-4-2-1, which he has used in 119 of those 189 games, including all four of Manchester United's fixtures in the Premier League so far this season.
He has used a 3-4-3 a total of 68 times, with the only other variation being 3-5-2, which he has used twice since 2020.
His three-at-the-back system brought him great success at Sporting, where he won two Primeira Liga titles in four years and gained a reputation as one of the most exciting managers in Europe. But it has been a different story so far at Manchester United.
Amorim's win rate in league games has plummeted from 77.2 per cent at Sporting to just 25.8 per cent at Manchester United, making it the lowest of any manager in the club's history.
Having taken just 31 points from his 31 games, Manchester United sit bottom among ever-present Premier League teams since his appointment, with twice as many losses (16) as wins (eight).
Why Amorim is in a minority
So how unusual is his system? Data for the last two decades gives a picture of how formations have evolved in the Premier League.
The favoured formation, by a considerable distance, is now 4-2-3-1, with 4-4-2 having dramatically declined in popularity. The 4-3-3 formation has also steadily increased in usage, albeit with a slight drop-off in the last two seasons.
The graph above shows an increase in popularity for Amorim's favoured 3-4-2-1, which was barely used prior to 2015 but became more popular with Chelsea's title win under Antonio Conte in 2016/17.
The formation is now at its peak in terms of usage in the Premier League, although that is largely due to Amorim's devotion to it.
He has used a back three in all of his 31 Premier League games but Crystal Palace and Wolves are the only other sides to have consistently used the system in that timeframe, ensuring Amorim's side remain in a minority in a league dominated by back fours.
The issues undermining his system
Crystal Palace's success under Oliver Glasner, having won the FA Cup last season and qualified for Europe on a modest budget, proves a 3-4-2-1 formation can work in today's Premier League, so why is it not happening for Amorim at Manchester United?
One issue is that they are still struggling to score goals. Despite spending more than £200m on the signings of Bryan Mbeumo, Matheus Cunha and Benjamin Sesko this summer, Amorim's side have only found the net four times in four games so far.
Amorim can feel confident that those players will improve their output as they settle but he needs more from his wing-backs too. Patrick Dorgu and Noussair Mazraoui, his starters at the Etihad Stadium on Sunday, have one Premier League assist and no goals between them in 52 Premier League appearances combined.
The worry is that Amorim doesn't have enough attacking potency among his wing-back options and it is similarly difficult to see an immediate solution to the side's issues out of possession, many of which stem from midfield, where Amorim is now using Bruno Fernandes as part of his two.
Fernandes' incisive passing allows Manchester United to launch quick attacks from the base of midfield but he is now spending less time in the areas in which he is most dangerous. His defensive deficiencies are also being punished routinely.
For Manchester City's first goal on Sunday, Fernandes switched off and left Phil Foden free to head in Jeremy Doku's cross.
The same lack of defensive awareness allowed Emile Smith Rowe to run beyond him and score Fulham's equaliser in the 1-1 draw at Craven Cottage last month, as shown below.
Fernandes is not the only one struggling in Amorim's midfield, with team-mates Casemiro, Manuel Ugarte and Kobbie Mainoo all lacking the athleticism to cope with the demands of the role.
Manchester City's second goal on Sunday, when Ugarte was dragged out of position to make an unsuccessful attempt to press Nico O'Reilly, showed how quickly they can become stretched.
"It's a problem and it's happening in a lot of the games that Manchester United are playing," said Sky Sports' Gary Neville.
"They start off really compact, where all 10 players are connected. Five at the back, two midfielders really close to that five, and then the three in front cuddling that two, so they are really protected.
"But if the game becomes a little stretched, which usually happens if Manchester United concede a goal, then those two look wide open and you can't deny that."
It doesn't help that the centre-backs behind them are reluctant to come out and press opposition players who get beyond the midfield, a weakness articulated by Alex Iwobi after that 1-1 draw against Fulham. "We knew that we would be able to get behind their two midfielders and their centre-backs wouldn't want to jump, so we exploited that," Iwobi told Sky Sports.
Fernandes has acknowledged the issue too. "We need people to be very aggressive in the moment of pressure," he told Sky Sports on Sunday. "We need to get the moments of jumping because if not the midfield gets every time overloaded.
"If you're not brave enough to do that, it's very difficult. They will find the gaps and the spaces to play because we're playing against a top team, we're not playing against a bad opponent."
And as Fulham and Burnley have already shown this season, it is not just the top teams who are punishing the weaknesses in Amorim's system. He has no plans to change but does he really have the personnel, either in midfield, or in his back three, or at wing-back, to make it work? Right now, their prospects do not look bright.
Last time's Between the Lines
We crunched the numbers on Premier League spending in the last edition of Between the Lines, unpicking some of the trends that defined a record-breaking summer transfer window.