Maria Sharapova blasted Serena Williams on Saturday for the American's controversial comments over a high-profile rape case, and even criticised the Wimbledon champion's colourful private life.
In an astonishing attack on the world number one, which comes just two days before Wimbledon gets underway, Sharapova told Williams to keep her opinions to herself as the bitter relationship between the two was laid bare.
Williams, the 16-time Grand Slam title-winner, was forced to apologise for her comments regarding the rape of a 16-year-old girl by two high school American football players in the Ohio town of Steubenville.
"I was definitely sad to hear what she had to say about the whole case," said Sharapova, who was defeated by Williams in the French Open final earlier this month.
"I just think she should be talking about her accomplishments, her achievements, rather than everything else that's just getting attention and controversy."
Sharapova, who has not beaten her great rival since 2004, also criticised Williams's love life after the American had aimed a thinly-disguised jibe at the Russian's affair with Bulgarian player, Grigor Dimitrov, believed to be a former Williams boyfriend.
"There are people who live, breathe and dress tennis. I mean, seriously, give it a rest," Williams told Rolling Stone magazine without naming the Russian.
"She begins every interview with 'I'm so happy. I'm so lucky' -- it's so boring. She's still not going to be invited to the cool parties. And, hey, if she wants to be with the guy with a black heart, go for it."
Sharapova, clearly upset at the insinuation, hit back on Saturday at Williams's romance with her French coach Patrick Mouratoglou.
"If she wants to talk about something personal, maybe she should talk about her relationship and her boyfriend that was married and is getting a divorce and has kids," said Sharapova.
"Talk about other things, but not draw attention to other things. She has so much in her life, many positives, and I think that's what it should be about."
Williams got involved in the Ohio rape case with her controversial remarks, also delivered to Rolling Stone.
"I'm not blaming the girl, but if you're a 16-year-old and you're drunk like that, your parents should teach you -- don't take drinks from other people," the magazine quoted Williams as saying.
"She's 16, why was she that drunk where she doesn't remember? It could have been much worse. She's lucky. Obviously I don't know, maybe she wasn't a virgin, but she shouldn't have put herself in that position, unless they slipped her something, then that's different."
On Wednesday, Williams, 31, apologised.
"What happened in Steubenville was a real shock for me. I was deeply saddened," Williams said.
"For someone to be raped, and at only 16, is such a horrible tragedy! For both families involved - that of the rape victim and of the accused.
"I am currently reaching out to the girl's family to let her know that I am deeply sorry for what was written in the Rolling Stone article. What was written -- what I supposedly said -- is insensitive and hurtful, and I by no means would say or insinuate that she was at all to blame."
Sharapova said she always make a point of trying to keep her private life under wraps.
"What I do on the court and what I talk about in my press conference is strictly about my career. I'm sure people want to know more, but yet I try to keep my personal life private," said the Russian.
"Nobody really cares about what I have to say, my opinions. If I speak to my friends, that's one thing. But I don't go out and try to create things that shouldn't be really talked about."
World number two, Victoria Azarenka, who is close friends with Williams but endures a cool relationship with Sharapova, refused to condemn the American.
"I have read her comments. I think there is always a benefit of a doubt to a person," said Azarenka.
"Only two people really know what happened. I know what it's like to be misunderstood sometimes. If I need some explanation from somebody, I'll go ask them directly.