Top-ranked defending champion Novak Djokovic, winner of the past three Grand Slam singles crowns, reached the quarter-finals of the $9.6 million hardcourt tournament with a 7-5, 6-3 victory over French 17th seed Richard Gasquet.
Novak Djokovic. Pic/AFP
The Serbian top seed will next face the winner of a later match between Spanish fifth seed David Ferrer and Argentina's 11th seed Juan Martin Del Potro.
"It's going to be very difficult. But I'm ready," Djokovic said. "I'm fresh physically, fit. Mentally I'm always there. I have a day off tomorrow, which gives me enough time to prepare for next challenge."
World No. 2 Nadal, a three-time Miami runner-up who has never lifted the trophy, ousted Japanese 16th seed Kei Nishikori 6-4, 6-4. Up next is French sixth seed Jo-Wilfried Tsonga, who ousted German Florian Mayer 6-3, 6-2.
Rafael Nadal. Pic/AFP
The Spaniard fired eight aces and won 65 percent of first-serve points while saving six of the eight break points he faced to advance in two hours and 11 minutes, improving to 16-3 on the season.
"The beginning was very tough," Nadal said. "I started playing more aggressively. At the end of the first set, I felt that I started to win my serves easier than him. I believe that I had more the control of the game.
"In the second set I started well. At 5-3, I didn't play my best game there and he broke me. Happy to have the break back later and finally win the match."
On the women's side, second seed Sharapova advanced with a 6-3, 6-0 victory over Chinese eighth seed Li Na, the Russian beauty snapping a four-match losing streak to the Asian star.
"I came into this match losing to her the last few times," Sharapova said. "I really wanted to change that."
Danish fourth seed Wozniacki ended the comeback run of US 10th seed Serena Williams 6-4, 6-4. The American had been sidelined from WTA events since the Australian Open due to an ankle injury.
"She definitely served the best she served in her career," Williams said. "She moved well and I just made too many errors. I felt a bit off. I probably played about 20 percent."
The frustration had Williams wanting to smash a racquet but she thought better of it, saying, "I thought about it, but I'm trying to be better now."
Sharapova, like Nadal a three-time Miami runner-up who has never won the crown, has a 3-2 record against Wozniacki.
"It's the semifinals, a tough stage and a tough opponent," Sharapova said. "Caroline has been one of the most consistent players on the tour for many reasons."
Sharapova's match began with five consecutive service breaks, but she found her form at 4-3, winning the last eight games of the match and 12 points in a row in one stretch to move on after 68 minutes.
"I was really consistent in conditions where it was a little gusty and blowing around and I faced a tough opponent too," Sharapova said. "I did a good job of maintaining my consistency throughout the whole match."
British fourth seed Andy Murray ousted French 13th seed Gilles Simon 6-3, 6-4. The Scotsman booked a last-eight date against Serbian ninth seed Janko Tipsarevic, who defeated Bulgaria's Grigor Dimitrov 7-6 (7/3), 6-2.
US eighth seed Mardy Fish outlasted Spanish 12th seed Nicolas Almagro 6-3, 6-7 (2/7), 6-3. Next for Fish will be Argentina's Juan Monaco, who eliminated American Andy Roddick 7-5, 6-0.