KEY BISCAYNE, FLA. (AP) - Rafael Nadal swept five consecutive games midway through the match, propelling him to a 6-4, 6-4 win over Kei Nishikori to reach the quarterfinals at the Sony Ericsson Open on Tuesday.
Nadal, a three-time runner-up at Key Biscayne, is seeking his first title in the tournament and his first anywhere since last year's French Open.
Second-ranked Nadal broke in the final game of the first set when Nishikori sailed an easy forehand long, then broke again and raced to a 3-love lead in the second set.
"At the end of the first set, I felt that I started to win my serves easier than him," Nadal said. "I had more the control of the game."
Nadal took a medical timeout late in the opening set to have his left leg wrapped by a trainer. He has been bothered by a sore knee since Indian Wells, where he lost to Roger Federer in the semifinals two weeks ago.
"I am not probably in perfect condition today with the left knee," he said. "But the important thing is to try to win as many matches as possible. For me this is an important tournament, and every victory has very, very big value for me, especially without being perfect."
Second-ranked Maria Sharapova became the first semifinalist when she drubbed reigning French Open champion Li Na 6-3, 6-0. Sharapova had lost their previous four meetings.
Like Nadal, Sharapova seeks her first Key Biscayne title. She lost the final in 2005, 2006 and last year.
Ninth-ranked Janko Tipsarevic made the quarterfinals by beating 20-year-old Grigor Dimitrov 7-6 (3), 6-2.