Most athletes are comfortable talking about injuries, so long as they can point to a bruise, a bandage, a cast or a spot on an X-ray. Some will even venture an educated guess at how long they might take to heal. Their mental health is a different story.

Or at least it was before Naomi Osaka ended a damaging standoff with top tennis officials by withdrawing from the French Open earlier this week, citing concerns for her well-being. It marked the first time a major star walked away from a major tournament without a visible injury. Judging by the reaction, it appeared Osaka landed on the third rail of sports.

Other athletes, notably Olympian Michael Phelps, spoke candidly about mental-health issues before. Some, like Los Angeles Lakers great Jerry West, detailed their struggles in books only after their playing days were long over. Still others wrestled that tortured secret for a lifetime.