Tennis star Coco Gauff has made a significant coaching change just days before the 2025 U.S. Open in New York. The 21-year-old American tennis player has parted ways with coach Matt Daly, while bringing in biomechanics expert Gavin MacMillan. This decision comes after Gauff’s inconsistent serve following her surprising first-round exit at Wimbledon. MacMillan, previously known for helping world number one Aryna Sabalenka improve her serve, is expected to make a positive impact on Gauff’s performance as she prepares for the U.S. Open.