The Herald Sun, owned by a News Corp subsidiary, published a defense of its cartoonist on the home page of its website, quoting Knight as saying: "The cartoon about Serena is about her poor behaviour on the day, not about race".
"That's what the cartoon was about, her poor behaviour on the court".
Knight told the interviewer that "the world has gone insane", and said that his wife and children were threatened on Instagram.
The Herald Sun reported on Tuesday that Knight had been mentioned on Twitter almost 74,000 times following the cartoon's publication.
Cartoonist Knight, whose cartoon appeared in Australian newspaper Herald Sun, depicted Serena as a huge baby stomping on her smashed racket and a baby dummy lay on the court beside her while Osaka is pictured as white and blonde despite her Japanese and Haitian heritage.
"Well done on reducing one of the greatest sportswomen alive to racist and sexist tropes and turning a second great sportswoman into a faceless prop", the author tweeted on Monday.
"Mark has the full support of everyone here".
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An indignant Williams emphatically defended herself, denying she had cheated.
He also Tweeted out the front page of the Herald Sun that reads, "If the self-appointed censors of Mark Knight get their way on his Serena Williams cartoon, our new politically correct life will be very boring indeed". In 2009, civil rights leaders and others criticized a New York Post cartoon that some interpreted as comparing President Barack Obama to a violent chimpanzee.
"Because I'm a woman, you're going to take this away from me?" she said. Backlash against the image included disgust from Melbourne politician Rohan Leppert, who wrote: "The racist vilification of Melburnians from the Herald Sun continues apace".
Wednesday's cover featured several of Knight's cartoons, alongside reasons why they might also have been considered offensive.
Williams is one of a small number of black female tennis players and is the most frequently drug-tested professional woman in the sport. It exaggerates her features in the way that - remember the cartoons we used to see of John Howard with the eyebrows, Tony Abbott's ears. I think the entire cartoon is just over the top, but the racism aspect of it is really what makes it repugnant.
"I don't believe them", the "Avengers" actor says.
Knight was criticised in some quarters for being "racist and sexist".