By Martyn Herman
LONDON (Reuters) - The heavy hitting shook the ground and the volume would have raised the Centre Court roof, had it been closed, as Serena Williams and Victoria Azarenka traded blows like a couple of prizefighters at Wimbledon on Tuesday.
A women's tournament that has seen title contenders fall feebly on the All England Club lawns, finally witnessed two grand slam champions going toe-to-toe in a thunderous encounter befitting the final, rather than the second Tuesday.
Williams eventually won 3-6 6-2 6-3 with her best tennis at this year's tournament so far to stay in line for a sixth Wimbledon title which would also complete the self-styled "Serena Slam", that is holding all four majors concurrently.
"I feel really vulnerable. I feel really vulnerable in a third set," Williams, who looked anything but, told reporters.
"At that point I kind of relax and whatever happens, happens."
Blocking her path to a first Wimbledon final since 2012 is Maria Sharapova after the Russian fought off feisty American CoCo Vandeweghe -- the only unseeded player in a quarter-final lineup few would have predicted at the start.
Sharapova won 6-3 6-7(3) 6-2 to set up another crack at Williams who she has lost to 16 times in a row since 2004 -- the year she beat the American to win her only Wimbledon title.
"I haven't played Serena here in 11 years," fourth seed Sharapova, who famously beat Williams to the title in 2004 as a 17-year-old, told reporters.
"That will be an incredible moment for me to step out on Centre Court against her again."
NEW FACES
The mayhem in the bottom half during the first seven days here gave a chance for some new faces to make their mark.
Garbine Muguruza seized the chance to become the first Spanish woman to reach the last four since Arantxa Sanchez-Vicario in 1997, beating Swiss Timea Bacsinszky 7-5 6-3.
American youngster Madison Keys was unable to unlock the defenses of 2012 runner-up Agnieszka Radwanska, though, losing 7-6(3) 3-6 6-3 with the Pole now facing Muguruza.
After a minute's silence on the 10th anniversary of the London Underground and bus bombings, followed by a short rain delay, play began on Court One with a one-set showdown.
Defending men's champion Novak Djokovic resumed against giant-serving Kevin Anderson after their fourth round clash had been stopped at two sets all on Monday because of bad light.
Top seed Djokovic survived some anxious moments and roared his frustration in the direction of a startled ball girl before edging his way to a 6-7(6) 6-7(6) 6-1 6-4 7-5 -- only the fourth time in his a career he has recovered from a two-set deficit.
INTENSE BATTLES
Williams and Azarenka have history, although not in any sinister sense. Both are fierce fighters and have contested some intense battles down the years, including two U.S. Open finals.
Former world number one Azarenka, seeded 23 but far more dangerous than that in reality, outplayed her opponent in a superb first set, absorbing the power of the Williams arsenal and punching back some spectacular winners.
When she sealed the first set with a clean-as-a-whistle forehand pass a fourth career win from 20 matches against Williams looked not only possible, but likely.
Azarenka was fired-up and raising the decibel level.
But then came the retaliation.
Williams, who narrowly escaped defeat by Briton Heather Watson in the third round on Friday, added a few clicks to her serve, beefed up her forehand and began bellowing "c'mons!" after winning big points.
Azarenka was taking some fearful punishment but somehow survived a Williams onslaught in an 18-point game at 1-2, saving three break points to level at 2-2.
The Belarussian had a break point in the next game but Williams responded with a backhand winner, held serve, and then won the next three games to level the match.
Sensing another semi-final, Williams marched ahead in the decider, banged down three consecutive aces to move 5-2 ahead and finished Azarenka off with three more in the final game.