The longevity meant full circle was bound to arrive at some point and Pep Guardiola now stands just as he did when touching down in Manchester: facing up against the pre-eminent Portuguese coach of a generation.

And this one might actually outlast him. It would take something spectacular for Ruben Amorim not to manage that but then this is Manchester United, when even the surest bets quickly escalate into blind chucks at black or red.

Guardiola has seen off three permanent United managers in his time at Manchester City. After Jose Mourinho, there was Ole Gunnar Solskjaer and now Erik ten Hag. Throw in Ralf Rangnick for good measure, too.

Mourinho's bite and snarl slithered under Guardiola's skin as they jousted in Spain yet an uneasy truce in England meant the sideshow was, largely, quashed. And when it comes down to pure football, there is only ever one winner.

That Mourinho only remained at Old Trafford for two years is something of a shame, because the awkward tension would have eventually snapped, and while Solskjaer delivered a blow or two to City, they often came too late to fundamentally matter.

But the arrival of Ruben Amorim promises to inject new life into a United side that so desperately needs it. But Amorim is seen as the proper coach to mount a challenge and is close to City's next director of football Hugo Viana in a way that will spark intrigue surrounding the relationships between the two clubs. City's Bernardo Silva was complimentary about the impact Amorim has had in Lisbon, on Monday night describing Sporting as a 'big machine right now'.

Tuesday's Champions League meeting might not offer insight into who has whose number, although how Amorim responds to any result - positive or negative - could set the tone for what will follow over the coming months. After all, the managers come up against each other again in little over a month's time at the Etihad Stadium.

'Pep is the best coach in the world,' Amorim said. 'I know it's tough for United fans, and I think City are the best team in the world.

'Every player is world class, it is always very difficult to predict what is going to happen. We have to be brave. I am a better coach than I was before. I think Pep is an even better coach. Today I have better players.'

Amorim was looking back on City's last trip here to the Portuguese capital two and a half years ago, pummelling their hosts 5-0 - ex-Benfica midfielder Silva particularly enjoying his brace, goading the home crowd - and leaving with Guardiola calling Sporting's Matheus Nunes - now at City - one of the best players in the world.

Plenty in Lisbon thought City would pinch their manager as well as their sporting director Viana who has been appointed Txiki Begiristain's successor at the Etihad.

Viana is banned from entering Sporting's dressing room on Tuesday, one imposed by Amorim before he accepted the job at Old Trafford. Silva laughed that he couldn't possibly wish Amorim well and is looking to settle scores with his mother and closest friends - all Sporting supporters - when he goes back to the Estadio Jose Alvalade.

'With a full squad we're always stronger,' Silva said. 'There is no denying that. We have unbelievable players missing. But also I don't like to find excuses. This club was never about that. Kevin (De Bruyne) was injured for six or seven months and we won the league. We always managed. Perform well individually and do your work. There are no excuses.'

What Silva references there is the troubling few weeks the Premier League champions have been dealing with. The injury issues have run deeper enough for Guardiola to request some play through the pain, a key message sent to more senior members of his squad before the surprising Premier League defeat by Bournemouth on Saturday.

Only three players - John Stones, Ruben Dias and Jack Grealish - have been left at home through injury but plenty more are on the wrong side of fully fit. De Bruyne went for just the one gentle jog down the touchline at the weekend; Kyle Walker came in to start from nowhere and it was plainly evident that he hadn't been around for a month.

Irrespective, Guardiola came out swinging at what he perceives as unjust criticism of performances. 'I know our standards, right?' he said. 'I know our standards. We lost one game in the Premier League.'

Guardiola on Facing New Managers

Guardiola, however, has a different perspective on the challenges posed by new managers. The City boss has consistently emphasized the learning experience he gains from facing different tactical approaches, particularly from those who are attempting to establish their own identities in the game.

He explained how facing new managers, with their fresh ideas and styles, pushes him to grow as a coach. Guardiola singled out Jurgen Klopp, his long-time rival at Liverpool, as a prime example of this learning curve. Guardiola's respect for Klopp's tactics and their intense battles have undeniably shaped his own coaching philosophy.

The City manager went on to highlight the influence of other managers, including Mikel Arteta (Arsenal), Unai Emery (Aston Villa), and even Andoni Iraola (Bournemouth). He acknowledged that while his most frequent encounters are with his direct rivals, the experiences he has with managers in other clubs, whom he faces fewer times, are still valuable. He believes that these encounters provide insights into different tactical trends and approaches that can help him evolve his own tactics and team strategies.

Guardiola's perspective on facing new managers highlights a key aspect of coaching excellence: a willingness to learn and adapt constantly. He recognizes that the landscape of football is constantly evolving, and that the only way to stay ahead of the curve is to continuously seek knowledge and inspiration from other coaches, even those who aren't direct competitors.

Guardiola's Focus on Bournemouth

While Guardiola acknowledges the significance of facing Ruben Amorim and Sporting Lisbon in the Champions League, he remains firmly focused on the upcoming Premier League clash against Bournemouth. He knows that Bournemouth, under the guidance of Andoni Iraola, will be a challenging opponent. He has emphasized that his primary concern lies in preparing his team to overcome this obstacle.

Despite the injuries plaguing his squad, Guardiola remains confident in his team's ability to perform. He pointed to the recent Carabao Cup match against Tottenham, where City lost despite a strong performance, as a testament to their fighting spirit and resilience. He is determined to see his team bounce back from the loss to Bournemouth and continue their quest for Premier League dominance.

Guardiola's words paint a picture of a manager who is not only seeking to achieve success but also eager to contribute to the growth and development of the game. His willingness to embrace the challenges posed by new managers and his constant pursuit of improvement exemplify the qualities of a true leader in football.