ALTHOUGH she has a strong claim to be regarded as the greatest tennis player of all time, Serena Williams is still only human, and in the past decade has beaten by many far more lowly-ranked players.

In all that time, however, she has never lost to the woman who is still regarded as her fiercest competitor - Maria Sharapova.

That remarkable record continued here in the semi-final, as Williams beat her old foe 6-2, 6-4 to go through to a meeting on Saturday with Garbine Muguruza of Spain. That's 18 wins out of 20 for Williams in all meetings between the two. Or 17 victories on the trot, if you prefer - Sharapova's only two wins in the series having both come as far back as 20004, the year she won here.

No matter the continent, whatever the surface, and irrespective of whether the match is in an early round or a final, Williams prevails. Her form can dip and her motivation slip against other opponents at other times, but put Sharapova on the other side of the net and she will be relentless and remorseless.

There is no love lost between the two, which is part of the reason why Williams always competes in such determined fashion against her Russian rival. But there is respect too, and that is another part of the reason.

Williams has had times when she has tired of tennis, when winning becomes too easy and perhaps even a bit boring, at least when she is up against humdrum opponents. It is never quite so easy against Sharapova, and their duels can never be classed as boring.

Sharapova knew she needed to be on top form from the off if she was to have a chance of ending her barren run, so it can only have been demoralising when her serve was broken in the opening game. She lost it again to go 4-1 down, and with a little over half an hour played she was a set behind.

Losing the first set is not the end of the world, of course, and Heather Watson showed in the third round that you can go behind to Williams yet still fight back to force the match deep into a third set. But for Sharapova to do that she needed to find something extra in her game while hoping that Williams' level of intensity would drop. What she did not need to do was serve a double fault when facing a break point for the first time in the second set. When she did exactly that, she went 3-2 behind, and the conclusion was in sight.

Sharapova threw everything she had into an attempted comeback, and it was noticeable that she began grunting more loudly in the second set. But once she was that break behind, the best she was able to do in what remained of the contest was save a couple more breaks. That only delayed the inevitable, and Williams served out with the match not even an hour and 20 minutes old.

"It's never easy to beat such a great player who's had such a wonderful career," Williams said graciously after the match when asked to explain her lengthy superiority over Sharapova. "So I don't know.

"Whenever you play someone that you know has beaten you before, you really get really focused, I think. That's what I do. Whenever I know I have to play Maria, I know I have to be focused, because she wasn't the best in the world for no reason."

The No 1 seed still refuses to talk about the potential Grand Slam that is now only a match away - she already holds the Australian, US and French Open titles - and that attitude may indicate a certain nervousness about being so close to that achievement. But she insisted that the key to her success so far in this tournament was the fact that she does not feel compelled to add to her haul of trophies.

"I've won so many Grand Slam titles, and I'm at a position where I don't need to win another Wimbledon. I could lose tomorrow.

"Sure, I won't be happy - but I don't need another Wimbledon title. I don't need another US Open. I don't need any titles to make it."

With five major titles herself, Sharapova has hardly had a poor career. But she has long come to accept that Williams is more capable of playing at a consistently higher level when it matters most. "I don't think it's a secret - I think she knows against certain players she needs to bring out her best," the No 4 seed said.

"The way that she plays [Victoria] Azarenka, myself, maybe a few others, she has to bring it on the line. We know we have to. We're not able to do that as consistent as she does."