Naomi Osaka was reduced to tears after a derogatory shout from a fan during her second-round defeat to Veronika Kudermetova at Indian Wells.
After being broken in the first game, a female fan taunted Osaka, who could later be seen wiping away tears as she slipped to a 6-0 6-4 loss against Kudermetova.
Following the match, the event's 2018 champion addressed the crowd, saying the incident reminded her of when Venus and Serena Williams were booed at the tournament in 2001.
"I've been heckled before and it didn't really bother me," Osaka said while holding back tears.
"But being heckled here. I've watched video of Venus and Serena get heckled here and if you've never watched it, you should watch it. And I don't know why, but it went into my head and got replayed a lot."
"I just want to say thank you and congratulations."
Osaka has been open about her struggles with mental health in the past and took a break from the sport following her upset loss at last year's US Open.
But the 24-year-old had said she was in a great place emotionally coming into the tournament.
Kudermetova closed out victory over the four-time Grand Slam champion, even when Osaka regrouped in the second set.
"It was a really tough match for me against Naomi," she said.
"She is a great player, she's a good fighter, and I'm really happy about my performance today. I was so focused and I'm so happy to be here and play in front of you guys."