(CNN) -- The Australian Open is known as the "Happy Slam." The players are usually re-energized after the off-season and gush over the way the tournament is organized.
But for the fourth day in a row in Melbourne, a multiple grand slam winner left the tournament without a smile on their face.
Following Serena Williams, Maria Sharapova and Novak Djokovic, two-time women's defending champion Victoria Azarenka became the latest big name bundled out when the Belorussian fell to Agnieszka Radwanska on Wednesday.
Yes, the upsets keep coming.
Radwanska not only defeated Azarenka in the quarterfinals to snap a seven-match losing streak against the world No. 2 but she didn't drop a game in the third set of the 6-1 5-7 6-0 victory.
When Azarenka misfired to seal her fate on match point, the crowd at Rod Laver Arena roared its approval.
With Djokovic departing Tuesday at the hands of Stanislas Wawrinka, it marked the first time in the Open Era both the men's and women's defending champions in Australia were eliminated at the quarterfinal stage.
"I think about today's match, what I did, what I could do better," Azarenka told reporters. "But other players, different vibe, whatever, I don't really care about that."
Radwanska meets Dominika Cibulkova in the semifinals Thursday after the diminutive Slovak -- who sent Sharapova packing -- cruised past maiden grand slam quarterfinalist Simona Halep 6-3 6-0.
"This is for sure one of the greatest matches at the slam, especially here," Radwanska told reporters. "(Azarenka) is playing great tennis here.
"Especially the third set was unbelievable. I really cannot complain about anything."
Li Na, the only grand slam champion in the women's semifinals and twice the Australian Open runner-up, battles Canadian upstart Eugenie Bouchard in the other semifinal.