This week marks four years since Jurgen Klopp's first game as Liverpool manager - and in that time he has 'transformed' the team, says David Maddock, the Daily Mirror's Northern Football Correspondent.
Klopp took over from Brendan Rodgers and oversaw a 0-0 draw at Tottenham on 17 October 2015 in his first game in charge of a youthful, inexperienced Liverpool team.
Since then, Klopp has overhauled the Reds' squad, led them to Champions League glory and turned the club into Premier League title contenders.
This Sunday, Klopp and his Liverpool players head to Old Trafford to face Manchester United, live on Sky Sports, with an eight-point lead at the top of the table over Manchester City. It's been some evolution.
"Of the 18 that were in the squad that day, only four are still at the club - that's Adam Lallana, Divock Origi, James Milner and Nathaniel Clyne. There's only eight who are still there from the 30-man squad he inherited," Maddock told Sunday Supplement.
How Liverpool lined up in Klopp's first game
Liverpool XI vs Spurs (17 Oct 2015): Mignolet, Clyne, Sakho, Skrtel, Moreno; Milner, Lucas, Can, Coutinho, Lallana; Origi
Subs: Bogdan, Toure, Randall, Allen, Ibe, Teixeira, Sinclair
"That actually shows not just how far Klopp has come but the incredible job he has done. He has transformed Liverpool back into a powerful force in European football, that is feared by some of the biggest sides in Europe. And he has made them into a credible title contender."
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Intensity and evolution
Klopp's Liverpool play with a characteristically intense pressing game and Maddock says there was evidence of that gameplan in his very first match in charge. However, since then, Klopp has recruited players who suit his preferred style better and also learnt to adapt his methods to the rigours of the Premier League.
"In that first game against Spurs, Liverpool ran 5km further than they had in any game all season. So straight away he had an impact - he was only there three days and he had an impact.
"He had to implement that very aggressive pressing, very aggressive running style.
"But in his first full season, they seemed to run out of steam a little bit by Christmas. They had a lot of criticism and there was a Dutch coach (Raymond Verheijen) who criticised him heavily, saying he's too demanding on players and he'll break them and his style can't work.
Klopp had a plan from the start... and it has evolved to make them into a top, top European side
"With the better players he's got in, with the bigger squad he's got he has refined that now so they still have that high energy pressing game but in a different way now. They're more targeted in the way they do that.
"Klopp had a plan from the start and you could not only see what the plan was, you could see it evolving over those four years. And it has evolved to make them into a top, top European side.
"That squad he inherited, I think it was much worse than the squad [Manchester United manager] Ole Gunnar Solskjaer has currently. Yet Klopp got them to two finals in his first season and since then he's got them in the Champions League every season."
The man manager
As well as finding players with the right physical and technical abilities to fit into his preferred approach, Klopp has also been careful with the types of personalities he has brought into his squad, says Maddock.
Creating a great team spirit - and a team of players who respond to his own personality - has been a priority for Klopp.
"I think his greatest quality is to find the right personalities," said Maddock. "People have overlooked this.
"They nearly signed Nabil Fekir from Lyon last summer and in the end the reason they didn't sign him was not because of the injury - and he did have an injury, which was a problem but they could have done the deal. There were other problems: he got his brother involved, began demanding more money, wouldn't speak to the Liverpool people. Klopp was like, 'we can't have that personality in our squad'.
I genuinely believe that fans at every club in the Premier League would want him as their manager
"He picks the right personalities who respond to his energy and his man management. You can see it. They believe. Virgil van Dijk says often 'this is special'. Klopp is responsible for that.
"I genuinely believe that fans at every club in the Premier League would want him as their manager. Even Manchester United fans have said 'we'd have loved to have Klopp as our manager' because he's a mix of this truly top class manager but also this personality that fans love as well.
"There are many reasons Liverpool are successful and it's not just Klopp. They have science, analytics which are ground breaking… but Klopp himself, his man management, his personality is a huge factor."
How to watch Manchester United vs Liverpool
Watch Manchester United vs Liverpool live on Super Sunday from 3pm on Sky Sports Premier League; kick-off 4.30pm.
Sky Sports customers can watch in-game clips in the live match blog on the Sky Sports website and app. Highlights will also be published on the Sky Sports digital platforms and the Sky Sports Football YouTube channel shortly after the final whistle.