Naomi Osaka returned to the US Open—the site of some of the tennis star’s greatest triumphs on a court and some difficult moments off it—for the first time in about a year to participate in a panel about mental health in sports, a topic she helped focus a spotlight on two years ago. “For me, coming back here means a lot.

This room, in particular. There were some tears shed. A lot,” Osaka, who won two of her four major championships at Flushing Meadows, said. Wednesday’s gathering, which also included Michael Phelps, a 23-time Olympic gold medalist swimmer, and US Surgeon General Vivek Murthy, touched on topics such as loneliness, connecting with others via a “buddy system,” the role of social media in mental health struggles and parenting.