World No. 2 Maria Sharapova defeated fellow Russian Ekaterina Makarova 6-4, 7-6 (7/3) at the WTA and ATP Miami hardcourt tournament on Monday to set up a quarter-final clash with China's Li Na.
Sharapova, the 2011 Miami runner-up, is chasing her first title at the event after finishing second three times. She lost in the final last year to Victoria Azarenka and in 2005 and 2006.
"I felt like I was up a set and a break, and played a bit sloppy," Sharapova said. "Combination of her stepping up, and being much more aggressive. She had opportunities, served for the second set.
"I just hung in there and stayed consistent. I played a much smarter tiebreaker, and I think that helped me."
Sharapova saved break point 11 of 15 times and converted on five of eight break point opportunities to advance into a matchup against Li, who rallied to beat Sabine Lisicki 3-6, 6-4, 6-2.
Sharapova double faulted 11 times but shrugged it off.
"Yeah, it's definitely not easy to play with that," Sharapova said. "But I managed to win the match in two sets, so that's a plus.
"Definitely consistency will be really important in the next match and getting the percentage up, and also returning a little bit better, little things here and there."
American 10th seed Serena Williams defeated Australian sixth seed Samantha Stosur 7-5, 6-3 in a rematch of the 2011 US Open final.
The 30-year-old Williams won 85 percent of her first serve points and converted four of her 13 break point opportunities in the one hour, 46 minute match.
In the final eight, Williams will face the winner between fourth seed Caroline Wozniacki and Yanina Wickmayer.
In men's action, world number one Novak Djokovic beat Viktor Troicki 6-3, 6-4 in an all-Serb matchup, Richard Gasquet of France stopped Albert Ramos 6-2, 5-7, 6-3 and Spaniard David Ferrer defeated Julien Benneteau 7-6 (7/5), 6-4.