They like Manchester band The Courteeners at Old Trafford.

Upon winning their 20th Premier League title fans had the words of their song 'Not Nineteen Forever' made into a banner that takes pride of place at the Theatre of Dreams.

But in the case of forgotten man Ander Herrera and his triumphant return to the side, the Middleton four-piece's earlier hit 'What Took You So Long?' would be more appropriate.

Ander Herrera (centre) is starting to make an impact for Louis van Gaal's Manchester United side

Herrera has forged a strong bond with fellow Spaniard Juan Mata, who scored twice against Liverpool

What took you so long Louis van Gaal? Why was Herrera, suddenly a key player in United's new-found swagger, out of the picture for long chunks of the season?

There is more than one answer.

Firstly, if anyone is a 'club signing' it is Herrera. Long before the coronation of King Louis, United originally vowed to ensure he would be their man following his mesmerising role in Athletic Bilbao' 2011-12 Europa League victory over Sir Alex Ferguson's side.

The admiration from within spread to the stands. They have never been shy of praising opponents at Old Trafford – this was where, in 2003, Ronaldo famously secured a standing ovation after a beautiful Champions League hat-trick for Real Madrid.

The 25-year-old was signed from Athletic Bilbao in a £28.8million move following Van Gaal's arrival

Herrera made a bright start to his United career, but injury saw the Spaniard sidelined for several weeks

In that frantic and ultimately fruitless first summer David Moyes famously made one attempt to capture Herrera's services which ended in confusion after the complex hurdles within the player's contract could not be overcome.

But they would not give up. When Van Gaal arrived talks were at an advanced stage with Herrera's representatives and he was happy to give the £28.8m move the green light with the new season approaching.

United have paid more for only four others, but as we have heard more than once, under Van Gaal's philosophy the fee counts for nothing.

Former United boss David Moyes made an attempt to capture Herrera's services, but failed

The Spanish midfielder is having to prove his worth to Van Gaal during his first season at Old Trafford

Herrera celebrates scoring during United's FA Cup fifth round victory against Preston in February

Not being the Dutchman's player, Herrera may have had to prove himself more than most. In a stuttering start to the season, he was not seen for a month after being substituted at half-time against West Bromwich Albion.

As late as February he had completed 90 minutes just once since the 5-3 humbling at Leicester City in September.

With their team struggling for rhythm United fans who remembered Herrera conducting the tune for Bilbao, scratched their heads at his continued absence.

When he made a rare start in the 3-1 FA Cup win at Deepdale on February 16 many put it down to Van Gaal's squad rotation.

Herrera's partnership with Daley Blind (right) has added tempo to what looked like a static midfield

But Herrera has started every game since, the kickstarting of his Old Trafford career coinciding with United finally clicking into gear.

His partnership with Daley Blind has added tempo to what looked like a static midfield. Suddenly United appear as sharp as their 1980s shirt sponsors.

Herrera's through ball for Juan Mata to open the scoring against Liverpool came in a dominant half of football United fans wondered if they would ever see again only weeks ago.

But there is more to it than Herrera simply not being the boss's signing.

In a wide-ranging interview with El Pais, he offered more clues.

Herrera and Mata chase down Philippe Coutinho during United's 2-1 victory against Liverpool on Sunday

Mata puts the ball past Simon Mignolet for his firs goal following a brilliant throughball from Herrera

'Van Gaal loves possession and doesn't like to risk [losing] the ball,' he said.

'He wants long possessions and to keep the ball because he believes you create spaces staying in the right place, because the team have the quality to find you.

'At the beginning he used to tell me off because I always looked for the ball, I wanted to have it, and I must wait for it.'

Van Gaal is on the record stating his belief that his players must not play off the cuff – that they should know their jobs and if they do them his side will win.

Michael Carrick (left) congratulates Herrera on the part he played in Mata's opening goal

It is a pragmatic cross-sports philosophy used in the NFL by New England Patriots head coach Bill Belichick, whose team this year won their fourth Super Bowl this century.

While it does not sound like the famous United Way, it certainly looked like it at Anfield.

Herrera, superb on Merseyside, believes that if it had not been for football he would have tried a career in sports journalism.