And during six years working alongside Carlo Ancelotti at Chelsea, Paris Saint-Germain, Real Madrid and Bayern Munich, Clement saw more than most.
Few left a stronger impression than Cristiano Ronaldo and Zlatan Ibrahimović.
“Two special people and characters as players were Zlatan and Cristiano,” Clement told Football Presse.
“Of course, everyone can see the special talent they are on the pitch but on a personal level they are also interesting, funny and confident.”
They were also very different personalities.
“Zlatan does it very openly, speaks very confidently — and at times it is arrogance, but that is what he is.”
Clement remembers one conversation at PSG particularly well.
“He used to be like that on a daily basis and would ask me questions such as: ‘What is Didier Drogba like?’
“I would go into detail about what he is good at and Zlatan would be like, ‘He is not as good as me’ and would make you laugh.”
Behind the bravado, however, Clement saw an elite professional.
“They were both very professional on and off the field. The way they looked after their bodies with recovery, knowledge of nutrition.”
But if Ronaldo's discipline was obsessive, Zlatan's influence on those around him could be intimidating.
“I never saw a personality or character so strong with his teammates. Frightening at times, but kind of in a good way.
“He was an ultimate professional, though.”
Clement remembers teammates who would shrink when Ibrahimović confronted them.
“I remember how strong Zlatan was with his team-mates. I have never seen anyone demand so much from his team-mates.
“Some other players were like shrinking violets and I felt for them. They were shaking in their boots when Zlatan had a go at them.”
Yet Clement would still choose the Swede if he were going into battle.
“I always think about him, kind of guy that you want to go into war with. If you're going into war, you want Zlatan next to you.”
At Real Madrid, meanwhile, Clement encountered Ronaldo at the absolute peak of his powers.
“I think Cristiano is the most talented player that I ever coached.”
The numbers remain extraordinary.
“In the first year he was at the club, 2013-2014. He scored 51 goals that season.”
The following season was even more remarkable.
“In the second year where we actually weren't as successful trophy-wise, he scored 60 goals.”
Clement was not surprised by Ronaldo's extraordinary longevity.
“The way he's looked after himself over his career — yeah, the way he's looked after himself over his career — it's not a surprise to me that he's still scoring goals and playing at a good level.”
At his Madrid home, Ronaldo had invested heavily in his physical preparation.
“At his house in Madrid, Cristiano had special recovery facilities that you would find at a club or a health spa. He had a cold plunge; he really invested in his profession and health.
“Those type of people go the extra mile.”
Clement also saw a different side to Ronaldo's relentless pursuit of goals.
“He understood his job and he understood how to help the team. And that was by scoring goals.
“He would get really annoyed if we had won the game, but he hadn't scored.”
That could sound selfish. Clement saw it differently.
“He saw his job as to score, and 'if I've not scored, I've not helped the team'.”
And despite the extraordinary ego that comes with being one of football's biggest stars, Clement regarded him as a good teammate.
“I think he was a good teammate. I do.”
There was also a tactical intelligence behind Ronaldo's success at Madrid.
Clement explained how Ancelotti built the famous BBC attack — Ronaldo, Karim Benzema and Gareth Bale — around the Portuguese forward's strengths.
“Carlo didn't want that with Ronaldo. He wanted to keep him as far up the pitch as possible.”
Madrid would attack in a 4-3-3, with Ronaldo on the left, Benzema through the middle and Bale on the right, but defend in a 4-4-2.
“It meant that Ronaldo could stay up, could stay forward and be the first line of pressure with Benzema.”
Benzema sacrificed more than the other two.
“He was a very, very unselfish striker, team player, a little bit like a Firmino type where he was a goal scorer, yes, but also a big provider.”
“And Ronaldo couldn't score 51 goals and 60 goals if Benzema wasn't that type of player.”
The contrast between the two remains clear to Clement.
“Cristiano, in terms of talent and performance, you know, no one better than him.”
But personality?
“Zlatan was the biggest personality. Strong, strong character.”
Three years after retiring from professional football, Ibrahimović remains deeply involved in Milan's world as a RedBird Operating Partner and Senior Advisor to the club's ownership and senior management. He also worked as a Fox Sports analyst during the 2026 World Cup.
Ronaldo, meanwhile, is still playing for Al-Nassr at 41. After captaining Portugal at his sixth World Cup, he has now admitted that the 2026-27 season will probably be his last.
Even retirement, however, will not mean disappearing.
“I have my future all mapped out,” Ronaldo said recently, with travel, padel and life away from football already in his plans.
Clement's verdict on the two men remains remarkably simple. One possessed the greatest talent he had coached. The other was the most imposing personality.
Both, ultimately, understood the same thing.
Talent gets you there.
The sacrifice keeps you there.