The Adidas Trionda World Cup ball is causing problems for goalkeepers due to a phenomenon called 'drag crisis,' according to an academic paper. Algeria goalkeeper Luca Zidane has conceded five goals in two matches, with shots from Lionel Messi and Jordan's Nizar al-Rashdan slipping through his fingers. Senegal's Édouard Mendy and Iraq's Ahmed Basil have also struggled to hold shots.
Joe Hart's observations and academic backing
Former England goalkeeper Joe Hart, commentating on the BBC, noted that goalkeepers are having trouble reading the ball's speed. 'The ball is coming into the keepers a lot faster than it feels when it comes off the foot,' Hart said. 'When goalkeepers get up to speed with these World Cup balls we're going to see these shots saved.'
A paper titled Orientation-Dependent Drag Crisis and Flight Response of the Fifa World Cup Match Ball Trionda by researchers from Seoul Women's University and the University of Tsukuba confirms Hart's view. The researchers fired the ball through a wind tunnel from six angles and found that at a certain velocity, the ball experiences drag crisis—where airflow shifts from smooth (laminar) to turbulent, reducing drag and increasing speed.
Design factors and variability
The study found that the Trionda's 'upstream seam and groove arrangements' enable drag crisis at lower speeds. The effect varies depending on whether the ball is struck on a seam or panel, with seams creating lower drag. Altitude also plays a role: higher altitudes reduce the likelihood of drag crisis.
Fifa highlighted the ball's four-panel construction, which includes 'intentionally deep seams' for 'optimal in-flight stability.' Adidas stated the Trionda underwent over 300 laboratory tests, ensuring a 'more predictable trajectory.' This contrasts with the 2010 Jabulani ball, which was smooth and criticized by goalkeepers like Iker Casillas and Gianluigi Buffon for erratic movement.
Impact on the tournament
The drag crisis primarily affects velocity rather than trajectory, according to the researchers. The paper, published in the journal Fluids, is freely available and may serve as a reference for goalkeepers adjusting to the ball.
