FC Barcelona fell at his feet. Again and again and again, from beginning to end.

There was a moment late in Wednesday's 0-0 clásico that summed it all up -- a portrait of a player and the night when, for the first time in 17 years and 48 matches going all the way back to the time someone threw a pig's head at Luis Figo, no one scored in a clásico. With 88 minutes, 38 seconds on the clock, Arturo Vidal speared a superb ball into Ansu Fati and he found Luis Suárez deep in the Real Madrid penalty area. Here, it seemed, was one last chance to shoot, yet just as the Uruguayan drew back his leg, he found Carlos Henrique Casemiro diving before him to block, another tackle made and another chance gone.

But that wasn't the moment, and this wasn't over yet. Two minutes later -- we're into the 91st minute now, when legs were heavy and smoke drifted across the stadium, Barcelona attacked once more. Leo Messi slipped the ball in to Suárez again, near the edge of the area. Before he had even had the chance to look down at it, it had gone. The ball and the game. Casemiro had tackled him with a backheel. This really was the last time; now it was over, no more chances. Barcelona's final attack had ended where it seemed like their every move had ended: at Casemiro's feet.

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At the whistle, Casemiro and Messi embraced. Messi had not scored; Casemiro had. "My goal is robbing the ball," he once said. On Wednesday night, it sometimes felt like he robbed all of them; the stats showed that no one completed more tackles. And yet his goal is more than just robbing the ball and when he had it, he played. He completed 67 passes, second only to Toni Kroos in the Madrid team, and he had more attempts on goal than anyone else too. His header, cleared off the line, was the closest Madrid came to scoring. Not just in any game: in the clásico... which was exactly the point.

It is not new, nor is it unknown -- sample headline from a couple of years ago: "life is hard without Casemiro" -- but there can rarely have been a better demonstration of just how fundamental the Brazilian is, nor any clearer vindication of his manager's methods, than in Wednesday's 0-0 draw.

Casemiro, right, kept Messi and Barcelona firmly in check en route to the first scoreless clasico since 2002. TF-Images/Getty Images

One day early in Zidane's first spell as Real Madrid manager, Casemiro knocked on his door. He hadn't played yet -- five games had passed -- and he wasn't happy. Play me, he said, please. Zidane looked at him, told him to calm down and said that once he started playing, he would never stop. Zidane was right, so much so that it became almost a running joke. After one game recently, Casemiro was asked if he was ever going to rest. By way of a response, he offered that cherubic smile he has and said something about how he didn't need it. Zidane didn't think so, either. You only ever leave Casemiro out to ensure that you can put him in.

Casemiro has appeared in every game and played every minute bar half an hour this season until Zidane had left him out of the team against Valencia on Sunday night, three days before the clásico. Even as the game slipped away from his Real side, the midfield increasingly controlled by Dani Parejo in a 1-1 draw, Zidane didn't put Casemiro back in, leaving him sitting there on the bench. Afterwards, reporters wanted to know why and three days later, they got their answer. Barcelona did not score at the Camp Nou for the first time in 34 games. That's why.

It was nothing to do with rest, and everything to do with risk.

Casemiro commits the fouls others don't and makes the tackles they won't. A lot of them. That smile, or something anyway, often gets him out of trouble -- the joke goes that he wears a cloak of invisibility, hiding his misdemeanours from referees -- but he can't avoid them forever. Going into last weekend, he had been on four yellow cards. A fifth and he would miss the next game. The next game was the clásico, one that tends to define the season. And that, Zidane had decided, was a risk far too great to take.

Every time you looked down at a Barcelona move ending and a Madrid move starting on Wednesday night, Casemiro was there, demonstrating why. At times, he appeared omnipresent. He was everywhere. Above all, he was everywhere his team needed him to be, which is pretty much where he always is.

Casemiro, left, has Zidane's complete and total trust to run the midfield. Zidane's job now is to figure out the right balance around him. PAUL ELLIS/AFP via Getty Images

Casemiro tells the story that he only became a defensive midfielder because he liked the odds. He could always adapt to different positions later and if there's one thing that defines him, it is that he adapts. At a trial when he was a kid, alongside 300 others, coaches asked who the forwards were. Fifty hands went up. Then they asked who was a No. 10. Another 50 hands went up. When they asked who the defensive midfielders were, eight hands went up. Casemiro saw his chance: less competition. "Me, I am," he said. He wasn't, but he is now, and Real Madrid love him for it.

Casemiro learned the role. Above all, he listened. Julen Lopetegui, his coach at Porto, described Casemiro's "secret" as the "desire to improve," his willingness to embrace advice, to do everything necessary, calling him "a joy to coach." Rodrygo says he is always telling him to go to the gym. He has regular sessions in an oxygen chamber and watches what he eats, obsessively, which seems appropriate somehow. "I fight for every ball as if it was a plate of food," he told Jorge Valdano recently.

There's something in that idea: as a kid, there wasn't much room at home and there wasn't much to eat either. Casemiro has talked about asking teammates to let him stay at their houses the night before games when he was young so that he could sleep properly, about how one of the best things about getting signing up for the youth system at Sao Paulo was that he was fed properly. And so, he went after that ball, doing the work that others didn't. Someone had to.

This week, El Pais writer David Álvarez told the story of how Casemiro was about to go on holiday in the summer when he found out that Madrid had just let in seven goals against Atlético Madrid. He unpacked his holiday bag and flew back, cutting short his break. His team needed him. That phrase defines him, and Zidane always knew as much. As a player, Zidane understood better than anyone how important Claude Makelele was; it is not by chance that when he decided to return to the French national team, he first called Makelele and convinced him to come too.

"Fundamental," Zidane has called Casemiro, and the Brazilian understands his role to a tee. "Casemiro covers the gaps," Casemiro said in an interview with El País a few years ago. "Casemiro has to cover the gaps left by the full-backs. Casemiro has to cover the gaps left by the midfielders. Casemiro has to cover the gaps left by everyone. That's balance for me; to make sure the game doesn't go mad. I don't have Isco's magic or Cristiano [Ronaldo]'s goals. I work."

That work helps Isco to have his magic. Helped Cristiano to score his goals. Valverde to run (and what a game he had on Wednesday). Benzema to play. Kroos to pass. Marcelo to attack. All of them to survive. Which is why they love him. "Centre-backs adore him," Lopetegui said. "He saved my life; I could play until I'm 45 with this guy by my side," Marcelo wrote. They all want him there, every minute of every game. There is only one reason for Casemiro to miss a match: if missing the next match is even worse.

Listen to Real Madrid's players and they fall at his feet. Watch Barcelona's players and so they do too.