Gauff hires MacMillan to fix serve after coaching change at US Open

Coco Gauff made a dramatic pre-tournament change and a nervy start to her U.S. Open campaign, parting ways with coach Matt Daly on the eve of the Grand Slam, hiring biomechanics specialist Gavin MacMillan to address chronic serving problems, and then scraping past Ajla Tomljanovic 6-4, 6-7(2), 7-5 in a nearly three-hour opener at Arthur Ashe Stadium on Tuesday night.

The moves were prompted by a glaring statistical weakness. Gauff entered New York having committed 320 double faults this season, the most on the WTA Tour by a wide margin, and she has averaged roughly 6.8 double faults per match. After the first-round win she added 10 more double faults and 59 unforced errors, and was broken six times, underlining why she felt compelled to change her backroom staff even at such a late stage. Gauff said she needed a "technical change" and did not want to "waste time continuing doing the wrong things," adding that the decision was "very sudden" because MacMillan became available.

MacMillan is best known for overhauling Aryna Sabalenka's serve in 2022, a transformation Sabalenka has credited with unlocking subsequent major success. Sabalenka told reporters she felt a difference within...