What Coco Gauff Is Doing to Fix Her Serve at the U.S. Open

The American tennis star has taken a proactive approach to repairing her most foundational shot.

Coco Gauff has employed a new coach to help with her serving woes. / Eric Bolte-Imagn Images

One of the great, gripping rivalries in 2025 women’s tennis is here, as Coco Gauff is pitted against her recalcitrant serve. The 21-year-old American struggled for the first five months of the year, got her groove back on clay where she picked up her second major at Roland Garros, and has stumbled since. While assorted players have been credited with various victories against her, the real culprit has been Gauff’s serve.  

Earlier this year in Montreal, she double-faulted 23 times against Danielle Collins. (Bear in mind: it takes 24 points to win an entire set.) And that was a match Gauff actually won. It’s a credit to her that she fights through these moments when her most foundational, fundamental shot deserts her. 

It is also a credit to her that she has attacked the problem head-on. 

Last week, on the eve of the major she won two years ago, she parted ways with her coach, Matt Daly, and hired a new coach, Gavin MacMillan. Coach is really a misnomer: MacMillan is less a rah-rah guy than a scientist, a sports biomechanics expert who believes performance peaks when technique peaks. 

Having played seven sports growing up in Canada, it’s fitting that he has worked with athletes ranging from Major League pitchers to MMA fighters to NFL players like Troy Polamalu. In tennis, MacMillan—a former college tennis player at San Jose State—is best known as the guy who helped Aryna Sabalenka overcome her serving woes. Instead of trafficking in sports psychology, MacMillan will stress balance, spinal stability and proprioception—the body’s sense of its position and movement in space. 

It remains to be seen how long it will take for the biomechanics to express themselves in Gauff’s service technique. Still, it’s hard to recall a player—never mind a top player—taking such a proactive approach to fixing such an obvious problem. Good for her for having the courage to try.

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