Paris St Germain's Thiago Silva reacts during their Champions League round of 16 second leg soccer match against Bayer Leverkusen at the Parc des Princes Stadium in Paris

Nobody seems to doubt Zlatan Ibrahimovic these days. Thirteen goals in 16 Champions League games for Paris Saint-Germain have undermined old claims that the striker could not perform on the biggest stage, and yet, curiously, it was the four that he scored in a friendly against England in 2012 that seemed to do most to rehabilitate his image. Perhaps because it was the British sporting press that had most stubbornly denied his gifts in the first place.

One way or another, the narrative leading into Chelsea’s Champions League quarter-final against PSG this week has been consistent. Wednesday night’s first leg will be Ibrahimovic vs Mourinho, the striker attempting to take down his former coach. L’Equipe carried both men’s images on their front cover, billing the encounter as “The Special Match”. Mourinho described Ibrahimovic during his pre-game press conference as “one of the three best players in the world”.

And yet, he might not even be the most important one in PSG’s starting XI. As much as Ibra has been the star of the show this season, with 40 goals in all competitions, any absence from the side on his part would only allow Edinson Cavani to slip into his preferred position in the centre of attack. The Uruguayan scored 104 goals in three seasons for Napoli in that role, including one against Chelsea in the 2011-12 Champions League.

Instead, the most difficult man for PSG to replace might be their captain. As a defender on a team that spends most of its league games encamped in the opposition half, Thiago Silva inevitably receives less attention than his colleagues up front. But while Ibra’s exact ranking among the world’s top forwards remains a subject of debate, the Brazilian has achieved far greater consensus. Simply put, he is the best centre-back on the planet.

That is the opinion of both his former manager, Carlo Ancelotti, and team-mate, Alessandro Nesta – two men who know a little something about the art. The latter named Silva 17 places ahead of the next best centre-back (David Luiz) in his submission for the Guardian’s top 100 players list in December. Ancelotti included the Brazilian ahead of Nesta when invited to draw up an all-star XI from a list of every footballer he had ever coached.

Silva’s quality was reflected in the fee that PSG paid to acquire him in the summer of 2012 – €42m plus bonuses. It was a record for Ligue 1 at the time, and, perhaps more poignantly, twice as much as they paid for Ibrahimovic. That was as it should be; a poll conducted by the Italian broadcaster Mediaset earlier in the summer had found that 75% of Milan fans would sooner give up their striker than the defender.

It has not all been plain sailing for Silva since then. Injuries have disrupted each of his two seasons in France so far, and in fact he is expected to play in a protective mask against Chelsea on Wednesday. He wore it for the first time during his team’s 1-0 win away to Nice on Friday, having damaged his nose during a collision with Lorient’s Vincent Aboubakar the previous weekend.

On Tuesday the magazine France Football sparked a minor furore when they revealed that such masks cost as much as €2,000 to purchase from the Madrid-based clinic that produces them. And yet, in some ways, the item provided the perfect visual analogy for Silva himself. At first glance, both player and mask might seem unassuming, but closer inspection reveals the qualities that make them so valuable.

While Silva’s facewear derives its value from high-end composite materials, the defender draws his from a lifetime of experiences on and off the pitch. Unlike so many of his peers, he was not a childhood prodigy – in fact, he nearly gave up on football altogether as a boy after disappointing trials with each of Flamengo, Fluminense and Vasco De Gama.

He could have quit and become a bus driver, or perhaps just collected passengers’ tickets on the one that his older brother was already operating. Silva certainly seemed to spend a lot of his time riding around on such vehicles. He even met his wife, Isabele, on a bus.

But something pushed him to keep pursuing his sporting dreams. He bounced through the youth systems of various smaller clubs before finally landing his first professional contract with RS Futebol, a minor club competing in regional competition. From there he was soon spotted by EC Juventude, and within a year sold on to Porto. Just like that, he was on his way to the big time.

Except, of course, that he was not. After a year in the Porto reserves, Silva was farmed out on loan to Dynamo Moscow, whereupon he contracted Tuberculosis. A late diagnosis almost cost him his life.

“I looked death in the face,” Silva would recall during one interview in 2011. “I had been sick for six months when the doctors worked out what I had. They told me that if we had left it another two weeks then there have been no possibility to find a cure. I was in hospital, I was eating a lot, but I didn’t even have the strength to walk.”

Instead, for a half a year he lay in bed, played Playstation and stared at Russian TV shows that he had no way to understand. That, and watched as much football as he could possibly find. He had always been an avid spectator of the game, right back to the years when, as a young child, he would sit on the sidelines at his local pitch, too shy to join in with the other boys.

But his was not a passive viewership. Silva was always learning, absorbing more about the game. Returning to Brazil after recovering from his illness in 2006, he had not played a competitive senior game in two years, and yet he soon won a starting place with Fluminense, quickly establishing himself as one of the best centre-backs in the country.

By December 2008 he was back in Europe, this time with Milan – although a complication regarding his status as a non-EU player meant that he would not be able to play a game until July of the following year. Once again he treated this set-back as an opportunity, devoting himself to studying the movements of Nesta and Paolo Maldini in training.

At home at night, he would carry on watching games from his native Brazil. “Every evening. Isabele is always complaining, saying: ‘You spend the whole day with the ball and now you are still watching games?’” he told Sportweek magazine. “But I tell her that if it was not for the ball I would still be in Brazil working as a bus driver.”

Instead he went from strength to strength, claiming a place alongside Nesta in Milan’s starting back line – which would become the pillar of the title-winning 2010-11 side. That same year he won the Armando Picchi award, given to the best defender in Serie A.

Through all those years of watching and learning, he had acquired the most important skills a defender can have – the ability to anticipate what will come next. Broad-shouldered and blessed with strong acceleration, even if not especially tall for his position, he had always owned the natural tools to be an effective defender, but it is the ease with which he reads the game that truly sets him apart.

He has demonstrated those skills many times over in Paris, despite the injuries that have kept him out of the line-up more often than he would like. Silva was PSG’s best-performer in their Champions League quarter-final against Barcelona last year, providing the catalyst for his team’s first-leg comeback when his header against the woodwork was prodded home by Zlatan Ibrahimovic. One of his tackles on Lionel Messi was so well-timed as to become an instant YouTube hit.

In the end, though, PSG still fell, exiting the competition on away goals after a 3-3 aggregate draw. Now they aim to go one better. The world’s attention will be on Ibrahimovic at the Parc des Princes, as he seeks a way through against Silva’s compatriot David Luiz. But Mourinho will know as well as anyone that his team’s greatest challenge might just lie at the other end of the pitch.