They will soon be rivals, but Erik ten Hag will have much to thank Manchester City boss Pep Guardiola for when he takes over as Manchester United manager this summer.
Ten Hag is poised to succeed Ralf Rangnick as United boss at the end of the season. He will move from Amsterdam to Manchester to take on a huge rebuilding job at Old Trafford, where Guardiola will become his main rival in the Premier League.
The 52-year-old Dutchman will have a major task on his hands, with Paul Pogba, Jesse Lingard and Edinson Cavani set to leave the club on free transfers, while many others face uncertain futures. United are about to finish their fifth successive season without silverware and Ten Hag will be expected to turn things around very quickly.
As former United defender Rio Ferdinand has explained, there are many facets to managing United. It is a completely different beast to Ajax, Utrecht or Go Ahead Eagles. "He's valued and looked at as a very good coach and he's coming in and he's risking that," Ferdinand said on his YouTube channel Vibe with Five this week.
"We've seen many managers now with far more experience, who have won much more than Ten Hag, bigger reputations, who have come in and been chewed up by this football club and spat out. And the players are still the same.
"So he has to find a way of getting in there and managing the characters, the personalities and the egos that are in there. And I know I sound like a broken record but the thing he has to do first is change the culture, bring the new culture and drive it. He has to do that, it's a massive part of if he's going to be successful."
As difficult as that sounds, Ferdinand was also quick to point out that Ten Hag does have some experience of working at a European giant, when he was manager of Bayern Munich's reserve team, from 2013 to 2015, when Guardiola was the first team's boss.
"He has been at the background at a big club - Bayern Munich are a huge club, one of the biggest in the world," Ferdinand added. "He was in the building at Bayern Munich when Pep was there. He understands what it is like at a big club with huge demands, something what Man United will be like. And most importantly he has been around big players, sat in the background and watched - seen how they are handled by Pep and his staff and seen how they react to certain situations. So he has the experience of being around big players."
Ten Hag didn't just work alongside Guardiola in Bavaria - he made it his mission to learn from him. The New York Times reported in 2019 that Ten Hag's office at Ajax has three pictures on the wall: Rinus Michels, the mastermind of Total Football at Ajax, Dutch legend and tactical innovator Johan Cruyff and veteran manager Louis van Gaal.
Aside from Total Football disciples, though, it is Guardiola who has had the biggest influence. "I learned a lot from Guardiola," Ten Hag said in February 2019 during Ajax's run to the Champions League semi-finals. "His philosophy is sensational, what he did in Barcelona, Bayern and now with Manchester City, that attacking and attractive style sees him win a lot. It's this structure that I've tried to implement with Ajax."
Before the Real Madrid tie that season Ten Hag credited Guardiola as an "innovator and inspiration" adding that the desire to "win by playing well" was a shared ideal. "Nobody will ever forget Guardiola. He has won so many trophies for a start - but it is mainly about how his teams play," Ten Hag added in 2020. "Guardiola only wants to win games with beautiful football, just like his teacher Johan Cruyff. And what makes him stand out is that he is proving his quality as a top coach in Spain, Germany and now England. He has adapted to the culture in every country."
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Ten Hag's other comments may not bode well for Cristiano Ronaldo. "Guardiola had great players at Barcelona, like Andreas Iniesta, Lionel Messi, Xavi and others," he explained two years ago. "But it takes a lot of quality from a coach to make top players play in a great way as a team. You have to convince them that they each have a role in that team. Guardiola is a master of that. Some top players cannot play in his teams - like Zlatan Ibrahimovic. Everyone has to contribute. The team comes first and not the individual."
Ferdinand's concerns about Ten Hag's ability to deal with all the exterior factors that come with managing a side of the magnitude of United may be allayed by the Dutchman's words on what he learned at Bayern.
"During my time at Bayern Munich, among other things, I saw how things work," Ten Hag said in a 2018 interview. "Every detail can be picked out for analysis. The media, people in general, always find something if you look for it. A hundred things can go right, if one thing goes wrong, people highlight it. That's the football world."
Ten Hag may not have managed a club like United before, but he has learned a great deal from Guardiola which should stand him in good stead at Old Trafford.