In late March, Nike introduced its latest collection of World Cup jerseys, receiving widespread acclaim from fans and commentators alike. The United States men’s national team showcased what many consider their most unique set of shirts in several decades, while other national teams, including those from France, England, Canada, and Uruguay, also garnered positive feedback.

However, during the recent international break when players donned these new kits for the first time, attention shifted to an unexpected issue: an unappealing bulge along the shoulder seam of the shirts. While the bulge was hardly noticeable on some designs, such as the US team’s striped home kit, it became quite prominent on others, including the sleek shirt worn by French star Kylian Mbappé, where it appeared almost absurd. Some players from Uruguay exhibited particularly noticeable seams, leading to comparisons with Shredder, the infamous antagonist from the Teenage Mutant Ninja Turtles, during a match against England.

Fans took to social media to express their concerns, with many reporting similar problems with their purchased jerseys. Some managed to reduce the bulge’s appearance by steaming the fabric or washing the jerseys prior to wear. However, others, including a Canadian supporter on Reddit, voiced stronger frustrations. “The way the shoulders are sewn together just makes them bunch like this no matter what,” the fan commented. “I think they might work if your shoulders are narrow – I have wider shoulders, and there’s just no way to prevent this shoulder line from bunching. This design is ridiculous.”

This issue is particularly significant for fans who invested between $100 and $200 in these jerseys, as well as for the national federations and athletes eager to present a polished image at the world’s premier sporting event. There were questions about whether Nike was addressing these concerns, and indeed they were.

Nike issued a statement to the Guardian acknowledging the shoulder seam issue and indicated they are exploring potential solutions. “During the recent international break, we noted a minor issue with our Nike national team kits, particularly around the shoulder seam,” a spokesperson stated. “While performance remains unaffected, the overall appearance is not up to our standards.”

This represents an unusual misstep for the prominent sportswear brand, which had previously highlighted the innovative design and technology of the kits upon their launch. The upcoming World Cup matches, set to take place in the US, Canada, and Mexico, are anticipated to be among the hottest in tournament history, a concern that was ostensibly addressed through the Aero-FIT design integrated into all authentic World Cup kits.

According to Nike’s marketing materials, Aero-FIT utilizes computational design and a specialized knitting process to help athletes maintain a cooler body temperature. A source familiar with the design process informed the Guardian that Nike’s approach is informed by performance data and incorporates artificial intelligence to assist their designers in product development.

On Tuesday, a source with knowledge of Nike’s launch stated that the company is currently in discussions with partner federations and vendors regarding potential next steps. It remains unclear if any redesigns of the kits will take place or what remedies, if any, will be offered to dissatisfied customers. Addressing these issues will pose significant logistical challenges, especially given the tight timeline as the World Cup approaches in just over two months, along with the large number of jerseys already sold.