MARTIN KEOWN: Manchester United have regressed under interim manager Ralf Rangnick

Whereas once Arsenal against Manchester United was an all-out battle between two giants striving to win the Premier League, on Saturday it’s a pair of clubs scrapping to finish fourth.

They remain embroiled in rebuilds — yet to recover from losing their two great leaders Arsene Wenger and Sir Alex Ferguson, who served as managers for a combined 48 years and won 55 trophies between them.

United have now announced that Erik ten Hag will be the next and fifth permanent manager since Ferguson to try to return them to former glories.

The two clubs are still rebuilding after the departures of Arsene Wenger and Sir Alex Ferguson

Ralf Rangnick’s interim stint hasn’t worked out. His coaching philosophy is similar to Jurgen Klopp’s. Rangnick believes pressing high up the pitch is the best way to win and there were articles lauding him as the ‘godfather of gegenpressing’ when he arrived.

But United simply do not have the players to play that way. Liverpool have bought meticulously and with Klopp’s style of play in mind. Luis Diaz is the latest example of this; his seamless introduction into the team being testament to the club’s homework.

United have instead targeted creative players over the years, with Bruno Fernandes and Paul Pogba more noted for their flair rather than their pressing.

But Rangnick arrived hell-bent on imposing his own footballing beliefs on to this group and failed to recognise the strengths and weaknesses of the squad.

Ralf Rangnick’s stint as interim manager at Old Trafford has not been a success

Failing to adjust the style of play to a squad’s strengths is as big a cardinal sin a manager can make.

He wanted to implement his high-pressing approach and it looked promising in his first match in charge — a 1-0 victory over Crystal Palace in which United won possession 12 times in the final third, their highest total in any game this season.

But it wasn’t sustainable. This isn’t a team of pressers. This isn’t a group with that defensive instinct, that desire to work hard and be organised and track back and take the ball.

Rangnick was once quoted as saying: ‘A little bit of pressing is like a little bit of pregnant. Either you are pregnant or not. Either you want to play pressing or not.’

When a good team presses, the defensive and midfield lines stay close together. They condense the space in between.

Luis Diaz is the latest example of smart recruitment from Liverpool and manager Jurgen Klopp

But when they lost 4-0 against Liverpool on Tuesday night, United allowed their opponents too much freedom between those lines.

The United defence — including Phil Jones after Rangnick made the questionable decision to hand him only his second start in 813 days — looked fearful and were continually dropping deep. Klopp exploited that, and the hosts’ opening goal saw Mohamed Salah and Trent Alexander-Arnold — two of the best creators in the business — all on their own on the right wing.

No one in a United shirt ran back with them and Liverpool were queueing up to cross the ball for Diaz to score.

Rangnick has to take his share of the blame for how this team have gone backwards rather than forwards since the sacking of Ole Gunnar Solskjaer last November. They managed just 28 per cent of possession at Anfield when this is a side that needs the ball to be effective.

United were often chasing shadows in their heavy 4-0 defeat to Liverpool at Anfield

It’s time for United to go back to the drawing board — and when buying, they need to do so with Ten Hag’s philosophy in mind. After that heavy loss to Liverpool, I’m expecting a reaction from United’s players against Arsenal today.

That’s a huge badge they wear on their chests and if nothing else, they need to play with pride and determination.

What has happened to Arsenal and United may serve as a cautionary tale for the two new frontrunners of English football — Manchester City and Liverpool. Guardiola and Klopp are the modern-day equivalent of the rivalry between Wenger and Ferguson.

Let this be a warning to City and Liverpool of what can happen to your club when you lose your great leader.

If you don’t retain the success when that leader is gone, it can take years to regain that winning formula.