MADRID -- Serena Williams cruised past No. 2 Maria Sharapova 6-1, 6-3 Friday to advance to the Madrid Open semifinals along with top-ranked Victoria Azarenka.
Williams sealed her seventh straight win over Sharapova with an emphatic slam on the new blue-clay court. Azarenka overcame a shaky start to beat French Open winner Li Na 3-6, 6-3, 6-3.
The ninth-ranked Williams opened strong, hitting six aces and earning two early breaks to take the first set.
Sharapova broke at love to even the score at 2-2 in the second set, but she quickly squandered her break with a costly sixth double-fault to fall behind for good.
Williams, who improved to 11-0 on clay this year, will face either U.S. Open champion Sam Stosur or Czech Lucie Hradecka.
After Azarenka struggled on serve early on, last year's runner-up found her stride and broke her Chinese opponent's first two service games of the second set en route to pulling even at a set each.
Azarenka, who has won four titles this season, then used her powerful groundstrokes to take a 4-0 lead in the decider before holding off Li's late charge.
"There are a lot of things that I had to change and come up with in order to surprise her because she was pretty unbelievable in the first set," said Azarenka. "I had to turn something around, I don't know if it was confidence or if it was self belief or just pushing myself to be better and really wanting to win the match."
Azarenka said she supported Rafael Nadal and Novak Djokovic in their criticism of the change away from red clay to the new surface.
"I do agree that it is very slippery. You feel unstable sometimes, actually, a lot of times," she said. "But right now there is no point on talking about it. After the tournament all the players can get together and discuss it."
The Belarusian will face Agnieszka Radwanska after she beat American Varvara Lepchenko 6-4, 6-4.
On the men's side, Argentina's Juan Martin del Potro hit 10 aces to beat Alexandr Dolgopolov of Ukraine 6-3, 6-4 and move on to a semifinal with Tomas Berdych.
Berdych dispatched Fernando Verdasco 6-1, 6-2, as the Spaniard made 24 unforced errors and showed little of the flare he displayed in the upset of the second-ranked Rafael Nadal on Friday.
Later, defending champion Novak Djokovic plays Serbian countryman Janko Tipsarevic before Roger Federer faces David Ferrer.