Azarenka, Sharapova in Indian Wells quarter-finals
Maria Sharapova stepped it up when she had to on Tuesday to set up an Indian Wells quarter-final clash with Sara Errani, a rematch of last year's French Open final.
Russia's Sharapova defeated Errani in straight sets in the championship match at Roland Garros to complete a career Grand Slam.
The Russian star, who won Indian Wells in 2006 and finished runner-up last year to Victoria Azarenka, started slowly against Spain's Lara Arruabarrena-Vecino but turned up the heat to win 7-5, 6-0.
Sharapova dropped her first service game to hand the Spaniard a 2-0 lead.
She then broke Arruabarrena-Vecino twice, but was broken again before winning the last three games of the opening set. From there she never looked back.
"I just didn't get a good rhythm on her game from the beginning," Sharapova said. "I think maybe I was going for the lines a little bit more than I had to, especially in the first few games when you don't know too much about your opponent or haven't played her.
"I thought towards the end of the first and beginning of the second set I really stepped it up, was being more aggressive and really gave myself a better margin than I did throughout the first set."
Sharapova delivered a stellar serving display in the second set, firing four of her five aces and never facing a break point.
Errani, who won the women's clay-court title in Acapulco in the build-up to Indian Wells, advanced with a 6-3, 6-2 victory over ninth-seeded Marion Bartoli of France.
"I think one of her biggest keys is her consistency and her ability to make her opponent play," Sharapova said of Errani. "She doesn't make many mistakes. You've really got to win the match out there."
Top-seeded Azarenka also advanced, shrugging off a sore ankle to beat Urszula Radwanska 6-3, 6-1.
Azarenka remained unbeaten in a 2013 season that has included an Australian Open triumph and a WTA title at Doha.
But the win over Radwanska, ranked 37th in the world, was tougher than the scoreline might suggest.
"I think it was pretty obvious that I wasn't feeling that well," said Azarenka, who had three double faults in dropping her serve in the fourth game of the opening set.
"My ankle was bothering me. It has been bothering me for a while, so it hasn't been really getting better.
"But on the bright side, I won the match," added Azarenka, who next faces eighth-seeded Caroline Wozniacki of Denmark.
Wozniacki, the 2011 Indian Wells winner, beat Russian Nadia Petrova 7-6 (7/3), 6-3.
Russian Maria Kirilenko upset third seed Agnieszka Radwanska 6-1, 4-6, 7-5. Kirilenko, seeking a second title of 2013 after her triumph in Pattaya City, will play former Wimbledon champion Petra Kvitova, the fifth seed, who beat Klara Zakapalova 6-2, 6-3.
Fourth-seeded Angelique Kerber of Germany and Aussie Samantha Stosur complete the quarter-final line-up.
Kerber defeated Spanish qualifier Garbine Muguruza 6-4, 7-5 and Stosur downed Germany's Mona Barthel 4-6, 6-2, 6-3.