Chess, not chance: Fluminense embrace underdog identity ahead of Club World Cup Semi-Final against Chelsea.

Fluminense manager Renato Gaúcho says tactical discipline and mental strength will be the keys to unlocking Chelsea, as the Brazilian side continues its impressive underdog run in the ongoing FIFA Club World Cup.

The Rio-based club, given just a 0.05% chance of lifting the trophy at the outset, now stands just one match away from the final. On Tuesday, they face Chelsea at the MetLife Stadium in New Jersey, aiming to defy yet another European powerhouse after knocking out Inter Milan and Al Hilal in the knockout stages.

Renato, 62, has become the face of Fluminense’s fairy-tale journey — animated on the touchline and unflinchingly honest in his assessments off it. But behind the charisma is a calculated strategist, fully aware of the size of the task ahead and what it will take to overcome it.

“This will be a chess match,” Renato said. “It’s not just about talent or flair. It will come down to positioning, decision-making, and above all, conserving energy. The heat, the timing — every detail matters.”

Fluminense were not expected to make it this far. Drawn into a challenging group alongside Borussia Dortmund, Mamelodi Sundowns, and Ulsan Hyundai, they were widely tipped to exit early. Instead, they held the German and South African sides to draws and beat Ulsan to advance.

But the real surprises came in the knockouts. A tactically resolute performance eliminated last season’s Champions League runners-up Inter Milan, before a gritty victory over Al Hilal in the quarterfinals. Now, Fluminense must navigate their toughest challenge yet—a Chelsea side still recovering from inconsistency but rich in resources and star power.

“Financially, we’re not even close. We’re maybe 10% the size of these big clubs,” Renato admitted. “But football isn’t always about money. Our focus, our discipline, and our will to fight — that’s what got us here.”

Fluminense’s story is not just one of grit; it’s also one of reinvention. When Renato returned to the club three months ago, relegation fears loomed large. Since then, he has restructured the team tactically, instilled belief, and adapted their style to suit the realities of competing against global giants.

The Brazilian side is expected to employ a ball-retention strategy to limit Chelsea’s transitions, while targeting key vulnerabilities in wide areas. Renato believes patience and precision will decide the match.

“If you’re constantly chasing the ball in 35-degree heat, you’re finished. Possession is not just a luxury — it’s a survival tactic.”

Chelsea manager Enzo Maresca is not taking their South American opponents lightly. Speaking ahead of the semi-final, the Italian praised the quality and intensity of Brazilian sides, citing his team’s previous encounters with Flamengo and Palmeiras.

“The quality of Brazilian football is exceptional,” Maresca said. “But it’s also their energy. They arrive fresher, hungrier, and they defend extremely well. This will be another very demanding game for us.”

Chelsea, despite their stature, have looked uneven throughout the tournament. A 3-1 loss to Flamengo in the group stage exposed their vulnerabilities, though they responded with a narrow 2-1 win over Palmeiras in the quarter-finals.

Still, Maresca knows that fatigue could be a factor as his squad—carrying the weight of a long European season—faces a fresher, highly motivated opponent playing without pressure.

For Fluminense, the pressure is already behind them. Everything from this point forward is history in the making.

“We’re not just here to participate,” Renato said. “We’re here to compete. We’ve come this far because we believe. And we believe we can go further.”