Serena Williams and Maria Sharapova reached the quarterfinals of the Mutua Madrid Open on Thursday. What does Sharapova need to do to take No.1 away from Williams? Find out here.
WTA Staff

MADRID, Spain - Serena Williams and Maria Sharapova moved through to the quarterfinals of the Mutua Madrid Open on Thursday, keeping the battle for the post-Madrid World No.1 ranking very alive.

Click here to watch highlights, interviews and more video from Madrid, all week!

The No.2-seeded Sharapova was the first to advance, cruising through the first set then winning a much tougher second set to close out Sabine Lisicki, 62 75. Not only was Sharapova down 3-1 in the second set, she also faced double set point serving at 4-5, 15-40 - but she clawed her way out of that game and, after six deuces, squeaked out one last break in the next game before serving it out.

"She's the kind of opponent that plays extremely well against top players - you can see that from her results, and she beat me last year at Wimbledon," Sharapova said. "This was our first meeting on clay, so a little different, but overall it was about keeping my intensity as much as I could. Maybe you're not going to play with intensity every point, but the more you do, the better chance you have of winning."

Sharapova Vs Lisicki Video: Match HIghlights | Sharapova Interview

The No.1-seeded Williams followed with a much simpler win over No.13 seed Maria Kirilenko, winning 10 of 11 games from 2-3 in the first set and never facing a break point to move on through, 63 61.

"I just felt really relaxed today - I was just taking my time," Williams said after the match. "I think the match was okay. I haven't had a chance to talk about it with my team yet, but I will. I'm a perfectionist - I always look for things I can try and do better. When we get together I'll see what I can do better."

Williams is now an incredible 25-1 on clay since the start of last year's clay court season. The World No.1 was asked in her post-match press conference what it takes to be a good clay court player.

"I think for one you have to be mentally strong, because you're going to play a lot of players that get a lot of balls back and you can't get frustrated," Williams said. "I also think you have to be fit to be able to do pretty good in the longer rallies on clay. And I think you have to be able to slide a little bit."

And what about taking some pace off your shots? "It's easy actually, because when you take pace off you don't hit it as hard and don't exhaust as much energy," she said. "Especially on the serve, I think it's a little easier. But it's really fun to hit a big serve and a big winner, too - both of them are fun."

Williams Vs Kirilenko Video: Match Highlights | Williams Interview

Williams' No.1 ranking is under threat this week - if Sharapova does one round better than her, she will take the top spot. That means if Williams loses in the quarterfinals, Sharapova will take it by reaching the semifinals; Williams semifinals, Sharapova final; and Williams final, Sharapova champion.