Coco Gauff's US Open title defense ended in a fourth-round loss to fellow American Emma Navarro, marked by 19 double faults and 60 unforced errors. Gauff's serve has been a significant weakness, with tennis coach Rick Macci diagnosing it as 'biomechanically disconnected' and suggesting it as an easy fix. The defeat has led to critical scrutiny from fans and experts alike, with some questioning her mental resilience and coaching support. Despite this, Gauff remains optimistic, acknowledging her need to overcome mental hurdles and improve her serve. Navarro will advance to face Paula Badosa in the quarterfinals. The loss also means Gauff will drop out of the WTA's top five rankings.