Serena Williams' withdrawal from next month's BNP Paribas Open at Indian Wells next month begs the question: Is her withdrawal due to a bad back or continued bad blood?

Williams has not played the Indian Wells, Calif., event since 2001, when her sister Venus pulled out of a semifinals match against her just four minutes before the match was to start. Serena was booed during the final against Kim Clijsters, and Venus and their father Richard were booed even more when they went Serena's box in the stands.

The family claims they heard racial slurs aimed at them and has boycotted the event ever since.

The Independent reported that Serena had softened her stance toward the tournament after watching the Nelson Mandela biopic Long Walk To Freedom and appeared poised for a return after her name appeared on the 2014 entry list.

Earlier this week, however, Williams said she wasn't coming, according to multiple media reports.

"After careful consideration, I will not return to the Indian Wells BNP Paribas Open this year. I send my best wishes to everyone involved with the tournament," Williams said in a statement. According to the Independent, she did not give a reason why.

Tennis.SI.com reported that Williams also pulled out of next week's Qatar Open because of a back injury she sustained between her second- and third-round matches in the Australian Open. Her coach, Patrick Mouratoglou said the pain was so bad that Williams considered pulling out of her third-round match against Daniela Hantuchova.

Williams won that match but then lost to Ana Ivanovic in the fourth round.

Publicly, no one knows for sure which of the issues is causing Serena to withdraw. Her silence, however, is another polarizing action that creates a widening game between her fans and her detractors.