Rafael Nadal, who received treatment several times for a nasty-looking blister on the palm of his left hand that he said caused him to serve slower than usual, advanced to a semifinal match against the winner of the marquee quarterfinal between Andy Murray and Roger Federer later Wednesday.
Azarenka won't have a semifinal date. No. 5-ranked Agnieszka Radwanska stopped Azarenka's 18-match winning run at Melbourne Park with a 6-1, 5-7, 6-0 win earlier in the day.
That means both defending champions went out in the quarterfinals - Novak Djokovic lost to Stan Wawrinka on Tuesday, ending his bid for a fourth consecutive men's title. Azarenka had been aiming for three in a row and other women's title contenders Serena Williams and Maria Sharapova didn't even make it as far as the quarterfinals.
Rafael Nadal won on his fourth match point on Dimitrov's serve in 3 hours, 37 minutes, a long time after his celebration following a second-set tiebreaker that more resembled a victory dance. He stayed in a squat position after his winning cross-court shot and then pumped his chest out three times.
There were more muted celebrations after a tiebreaker in the third set, with Rafael Nadal acknowledging Dimitrov let him off the hook with a wide forehand on set point.
"It's a tough moment mentally for an opponent,'' Rafael Nadal said. "If that forehand from him goes in and he wins the third, I'm going to be fighting.''
Rafael Nadal fended off three set points in the third set, including two in the tiebreaker, and won on his first set point.
He went up 2-0 in the fourth when he hit a passing backhand down the line on break point with Dimitrov standing at the net. At the end, Dimitrov appeared to wipe tears from his eyes with a towel as he walked off Rod Laver Arena.
Dimitrov was still emotional during his post-match news conference, tearing up while discussing the forehand that got away.
"Obviously I got to put that in the past,'' he said. I'm sure I could have done something different. But in a match everything comes down to a split of a second ... whether in or out.''
Earlier, he said: "I'm a bit shattered. I came out expecting nothing less than to win.''
Azarenka's defeat left 2011 French Open champion Li Na as the only major winner remaining in the women's draw. Radwanska next plays No. 20 Dominika Cibulkova, who won the last eight games in a one-hour, 6-3, 6-0 quarterfinal rout of No. 11-seeded Simona Halep earlier Wednesday.
Li, a two-time finalist in Australia, will play 19-year-old Canadian Eugenie Bouchard in the other semifinal.
Radwanska played drop shots and slices from the baseline, forcing Azarenka to come forward and then lobbing or passing her. She hit touch volleys with calm precision, and instinctively anticipated Azarenka's shots.
"She was aggressive. She was making everything. She was guessing right,'' Azarenka said. "I was just playing a little bit too predictably.
Radwanska was also safe on her own serve, dropping just two games while breaking Azarenka six times. She hadn't beaten Azarenka in their last seven matches.
"I said to myself one day I have to have one step forward and do the semifinal, and I'm so, so happy that I did it finally,'' Radwanska said.
Azarenka was booed late in the match when she smashed a ball into the back of the court after another one of her 47 unforced errors. She screamed loudly after losing big points to the incredibly consistent Radwanska, punched her thigh and her racket and even slapped the court with her hand. Nothing worked to change her fortunes.
"I'm not happy with what I did today, but on the court I felt like I could have played a lot better,'' Azarenka said. "I can't take away what she's done today. She played amazing.''