The US Open has produced some of tennis's most memorable moments, but it has also delivered a number of stunning first-round shocks. Few results were more surprising than Emma Raducanu's defeat to Alize Cornet in 2022. Just a year earlier, Raducanu had become the darling of tennis, winning the US Open as an 18-year-old qualifier. But her return to Flushing Meadows was a very different story. Raducanu was beaten 6-3, 6-3 by the No. 40-ranked Cornet. The defeat made Raducanu just the third defending women's champion in the Open Era to lose in the opening round the following year. Elena Rybakina suffered another major shock that same year. The No. 25 seed had won Wimbledon just weeks earlier and arrived in New York as one of the title favorites. However, qualifier Clara Burel delivered the biggest win of her career, beating Rybakina 6-4, 6-4. The Kazakh struggled throughout, making 37 unforced errors and converting just one of nine break points. Taylor Fritz also saw his title hopes end immediately. The No. 10 seed and top-ranked American had reached the Top 15 and won Indian Wells earlier that year. But qualifier Brandon Holt, the son of two-time US Open champion Tracy Austin, pulled off a stunning 6-7, 7-6, 6-3, 6-4 victory to slash Fritz's hopes. Novak Djokovic's defeat to Mariano Navone in 2026 was perhaps the biggest shock. The 24-time Grand Slam champion struggled physically in the humid New York conditions before losing 7-6, 5-7, 4-6, 6-2, 6-1. It was Djokovic's first-ever US Open first-round defeat and his first Grand Slam opening-round loss since 2006.