When Jurgen Klopp was sizing up his first opponent as Liverpool manager -- Mauricio Pochettino's Tottenham -- in October 2015, he was in awe of their continuity and clear on-pitch identity. "They've worked together for some time and are fine-tuned," he said. "They have a style they are convinced about, and they give it everything."

The German was expected to deliver those very elements at Anfield by Liverpool's owners, Fenway Sports Group. They didn't set him targets based on league position or European football, recognising the reconstruction job stretched far wider than those remits. Klopp needed to change more than results. He was required to create a unique culture at the club that observers could immediately tie to the Merseysiders, making it easy to distinguish their hallmarks as was the case with Pochettino's young, high-pressing Spurs.

It is poetic, then, that Klopp's crowning moment thus far as Liverpool manager, when his side lifted the European Cup on the back of a 97-point league season having lost the Champions League final a year earlier, came against Tottenham in June.

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That showpiece game in Madrid, decided by goals from Mohamed Salah and Divock Origi, felt like a springboard for Liverpool but a full stop for their opponents. Ahead of this Sunday's clash at Anfield, there's a real sense that as one era is just getting started, the other might be coming to an end.

It was a miracle born out of masterful coaching that took Spurs to the final; they had a net spend of just £29 million since Pochettino's appointment in 2014 through the start of the January transfer window. For perspective, the comparison for the same period: Manchester City £518m, Manchester United £466m, Arsenal £225m, Chelsea £200m and Liverpool £183m.

Tottenham have the lowest wage bill of the "big six" clubs and became the first Premier League team to not make a signing for an entire season (2019-20). Pochettino was massively overperforming in relation to his spending power and naturally began to wonder how he was going to continue trying to compete with City and Liverpool when Pep Guardiola and Klopp have surgically moulded their squads as Tottenham cry out for a much-needed refresh.

Ahead of the Champions League final, Pochettino issued a warning about this very scenario.

"In the five years we have achieved a lot of things, and I think like I explained before, it was an amazing period. But now it's what's next. I think of course we are all excited now and it's difficult to see the future, but the future arrives quick. If you are not focused and if you don't start to work and if you do not make a plan, if you don't anticipate the things, when you crash, you crash.

"If we believe that if we operate in the same way that we have operated in the last five years we are going to be every season in the final of the Champions League, and we are going to be every season in the top four and competing against projects like Liverpool or Manchester City, I think we are very naive. If you want to expect the same from Liverpool, from Manchester City or Manchester United and Chelsea, and you put the same expectation on Tottenham, and the people expect the same, of course, give me different tools to work [with]."

Spurs, who travel to Anfield on Sunday with Pochettino now the one envious of the house Klopp has built, have been shambolic this season. They were dumped from the League Cup by Colchester on penalties, decimated in a 7-2 drubbing at home to Bayern Munich in the Champions League and have suffered top-flight defeats to Newcastle and Brighton, the latter coming by a three-goal margin.

There is an argument that the Spurs boss was backed with funds this summer given the additions of Tanguy Ndombele, Giovani Lo Celso and Ryan Sessegnon and should be taking the team to elevated levels. Yet it ignores the reality that the recruitments, part of the manager's wish list submitted after defeat in the Champions League final, only arrived late in the window. They were not afforded a pre-season to acclimatise to the 47-year-old's demands and have struggled with injuries. Equally, the kind of "reset" Pochettino had hoped for is as much about outgoings as it is about new faces.

Take the matchday squads when Klopp's Liverpool and Pochettino's Spurs collided four years ago. Only four players of Liverpool's matchday 18 remain at Anfield: James Milner, Adam Lallana, Divock Origi and Nathaniel Clyne, who would have moved on in search of greater game time had he not suffered an ACL injury in July. By contrast, 11 are still at Tottenham: Hugo Lloris, Toby Alderweireld, Jan Vertonghen, Danny Rose, Dele Alli, Erik Lamela, Christian Eriksen, Harry Kane, Michel Vorm, Harry Winks and Ben Davies. Their roster is not only stale, but it contains too many players who have been open about testing themselves elsewhere and have actively sought moves away.

Another issue is the familiarity with disappointment. Spurs have lost two FA Cup semifinals, to Chelsea and United, as well as the League Cup final to the Blues when Mourinho was in charge at Stamford Bridge in March 2015. In January, their depleted side was beaten on penalties by Chelsea again -- this time under Maurizio Sarri's watch -- in the last four of the same competition. Then came the loss to Liverpool in Madrid, and when you throw in a second-place finish in the league in 2016-17, it is hard to imagine how a group of players that have had so many nearly moments can go again without a real shake-up.

Why would they believe they can do any better than they have already done?

When Klopp's charges surrendered the League Cup and Europa League to Manchester City on penalties and Sevilla, respectively, in 2016, Sadio Mane, Georginio Wijnaldum, Joel Matip and goalkeeper Loris Karius were brought in that summer. Liverpool subsequently qualified for the Champions League and brought in Mohamed Salah, Andy Robertson and Alex Oxlade-Chamberlain, with Virgil van Dijk joining in the winter as Philippe Coutinho left for Barcelona. The Reds reached the final of the continental tournament in 2018 and responded to that 3-1 loss to Real by upgrading from Karius with Alisson, while Fabinho and Naby Keita bolstered their midfield options and Xherdan Shaqiri offered attacking depth.

While Klopp has had the power to reshape Liverpool, Pochettino has been at war with stasis.

Tottenham have exceptional facilities: their stadium is arguably the best in Europe in terms of design and function, while their training complex is also on the cutting edge. Chairman Daniel Levy has made them sustainable and has helped Spurs develop into much more than a mere nuisance to rivals Arsenal. In doing so, his side have claimed a seat at the top table, but they have also reached a comfort zone, and that is largely due to the structure, which is designed to try to keep pace rather than set it.

Pochettino has persistently demonstrated his ability to unearth solutions, but how do you remedy the end of a cycle under constant constraints?

Following Spurs' 5-0 Champions League victory over Red Star Belgrade on Tuesday, a win at Anfield, where Liverpool have not lost in 44 top-flight fixtures, could provide a short-term tonic. However, Tottenham have not picked up maximum points on their last 10 Premier League trips and really should have paid attention to Pochettino's "when you crash, you crash" caution.