World number one Victoria Azarenka continued her stunning start to the year by thrashing Poland's fifth seed Agnieszka Radwanska in Indian Wells.
The Belarusian powered to a 6-0 6-2 win over Radwanska, who has the second-best record in 2012 after Azarenka.
"I was really impressed with the way I played today," Azarenka, who has won all 21 of her matches this year.
Novak Djokovic, Rafael Nadal and Roger Federer all made it through to the quarter-finals in the men's draw.
World number one Djokovic dropped his first set of the tournament before seeing off Spaniard Pablo Andujar 6-0 6-7 (5-7) 6-2 and he next faces Spaniard Nicolas Almagro, who beat Tomas Berdych 6-4 6-0.
"In the end I was lucky to get through some points," said Djokovic. "I think I played one of my better sets in the last couple months in the first set but he surprised me with his aggressive approach.
"In the second set I started playing a little bit more defensive and that allowed him to come back into the match but in the third set I regrouped. I managed to stay calm mentally and find my rhythm again."
Federer, who next faces Argentina's 2009 US Open champion Juan Martin del Potro , has been battling flu and a temperature in the ATP event that he has won three times.
He battled past Brazilian Thomaz Bellucci 3-6 6-3 6-4, but said: "I'm still hurting a bit but at least I don't have a massive headache, aches and pains any more.
"That's all gone now. I got maybe a bit lucky but it's taken some time to for me to get better, to be honest. I thought I would see quicker improvements."
Nadal's 6-3 6-2 win over 21st seed Alexandr Dolgopolov came in in just 76 minutes and saw him successfully challenge a call to reach match point, which he won when Dolgopolov hit a forehand long.
"He is very difficult to play against," said Nadal. "He can produce winners from every part of the court. He's a funny player, good for tennis."
The Spaniard next faces Argentina's unseeded David Nalbandian , who came from behind to shock sixth-seeded Frenchman Jo-Wilfried Tsonga 3-6 7-5 6-3.
Radwanska has lost just four times in 2012 but each of those defeats came against Azarenka, who said: "I didn't expect to win that way. I'm proud how I fought hard and played winning tennis.
"I had very good motivation because I knew she's an excellent player, so I had to come up with a great match today.
"I was just really focused on every moment, on every point I played, on every ball I was striking. I didn't really think about the score."
The Belarusian will face Angelique Kerber in the semis after the German shocked French Open champion Li Na of China 6-4 6-2.
The eighth seed, who lost in after one hour 23 minutes, said: "My serve didn't work. The three times I played her before I was getting points on my serve but today was different."