The last time Serena Williams and Caroline Wozniacki collided, it was at the U.S. Open. Williams schooled the former world number one en route to the final. Tonight, in the quarterfinals at the Sony Ericsson Open, Wozniacki recorded her maiden win over the multiple majors champion. The Dane sent Williams packing 6-4, 6-4 to advance to her initial semifinal in Miami.

The two had battled on three previous occasions with Williams the victor. Following comfortable holds by both players, Williams saw a winner fly by to set up break point for her opponent. Wozniacki capitalized thanks to an errant forehand from Williams.

Despite striking only four winners in the first set, the single break of serve was adequate for Wozniacki to go on to capture the opening set.

The second set, on a forehand sliced into the net by Williams, Wozniacki arrived at triple break point. The Dane connected on a forehand pass for a winner to put herself ahead 2-1.

Later, courtesy of a spate of miscues by Williams, Wozniacki banked a second break to stretch her lead to 5-1.

After Williams held, she manufactured her first break points of the evening and was able to convert. Then by guarding serve, Williams narrowed the deficit to 4-5 putting pressure on her counterpart to close out the match.

Serving for the semifinals, Wozniacki got to 30 all. Next, with Williams flubbing a return, Wozniacki had match point. Soon, the session ended with Williams dumping another backhand into the net permitting Wozniacki to move on.

No doubt, Williams was the aggressor while Wozniacki was a backboard as usual. Comparatively, Williams had 34 winners and 36 unforced errors as to Wozniacki who had 12 winners and 13 unforced errors.

Williams was not at her best particularly on serve despite having a high percentage when asked she responded “I probably could have gone for more. I was going for [a higher] percentage of first serves, but that’s not my game. I just want to play my game that I am used to and what I do best”.

At times, Williams seemed somewhat over eager and appearing to gesture to herself to calm down. Consequently, was she anxious? Williams replied “Just telling myself to relax and not crack, you know, a racquet” after which she smiled.

Williams did not take her opponent for granted saying “everyone I play always plays the match of the year. It’s no surprise. I think that she knew that she had to play really well to hang in there. I didn’t step up to the plate”.

Shot selection was an issue approaching on balls which landed in the middle of the court, then being readily passed. Williams answered “I probably could have done that better. The good thing is I could have played a lot better. I probably played about 20%. . . It would really suck if I had to sit here and say I couldn’t do any better. That’s not the case”.

Williams expounded on why she said twenty percent “I just made a tremendous amount of errors. There’s no reason for that. I’m older and I shouldn’t do that. There’s no excuse. I just gotta stop that”.

Wozniacki was thrilled to with the outcome. The Dane expressed that the key was “I think I served well today. I think my first serve in particular was good. First time I played against her I had match points and lost 76 in the third, so I knew that I had to do something. I had to serve well to close the match out because she wasn’t going to give me anything”.

At one point Wozniacki had more aces than Williams which was a revelation. When asked whether this was a surprise, Wozniacki countered “Oh, did I? Well, that would surprise me, yes” and grinned.

No longer ranked number one, Wozniacki has been a sleeper at this tournament. Although it’s great to be number one, is it helpful to fly under the radar of late? Wozniacki cited “yeah, I don’t mind. I can see now that the draw I have has been pretty tough. I could have met [Kim] Clijsters but I played [Yanina] Wickmayer, who also played some very good tennis. Then Serena in the quarters and Maria [Sharapova] in the semis. It’s not easy, but I’m just pleased. I just take always one match at a time. Any court is the same. If people talk about me or not, to be honest, as long as I win, I’m happy”.

Wozniacki will battle Sharapova for her first berth in the final at the Sony Ericsson Open. Sharapova leads in their head to head 3-2.