AUSTRALIAN Open champion Rafa Nadal said he felt sorry for Naomi Osaka after she was rattled by a heckler during her second-round loss on Saturday night at Indian Wells, but added that tennis players needed to be ready to deal with adversities.

Osaka, who sparked a conversation about mental health in sports last year with her withdrawal from the French Open, was thrown off her game and began to cry after a person screamed, "Naomi, you suck!" early on in her 6-0 6-4 loss to Veronika Kudermetova.

After the match, Osaka spoke directly to the otherwise supportive crowd, saying the incident reminded her of the abuse Venus and Serena Williams received at the tournament in 2001, which led them to boycott the event for more than a decade. 

"In the real world, that happens, you know? I feel very sorry for her," Nadal said after his 7-5 6-3 win over Daniel Evans on Monday. "We are very lucky people that we're able to enjoy amazing experiences ... because we are tennis players.

"Even if is terrible to hear ... we need to be prepared for that, no? We need to resist these kind of issues that can happen when you are exposed to the people. Nothing is perfect in this life, no? We need to be ready for adversities.

"I understand that probably Naomi suffered a lot with these kind of issues that she has, mental (health) issues. The only thing that I wish her is recover well from that and wish her all the very best."

Daniil Medvedev said he could understand Osaka's response to the heckling after he himself was booed and heckled by sections of the shamelessly pro-Nadal crowd during the Australian Open final in January. 

"I felt not great in Australia," Medvedev said after his loss to Gael Monfils. "I can feel the fans that maybe say, what the hell? They're (players) getting millions. They should be ready for everything.

"At the same time we're humans. Sometimes we feel bad. Sometimes we feel good. I can understand that Naomi didn't feel that great when she heard it and I can completely understand her feelings."