LONDON (Reuters) - The needle on the Wimbledon Richter scale sat poised and ready but Serena Williams dug deep into her battle-hardened playbook to ensure there was no earth-shuddering shock at the hands of scurrying Briton Heather Watson on Friday.
With the shockwaves of Rafa Nadal's exit at the hands of maverick journeyman Dustin Brown 24 hours earlier still rippling around the All England Club, Williams stood on the brink of an even more astonishing reverse.
The five times champion was two breaks down in the third set to her 59th-ranked foe and at one stage stood two points from defeat before normal order was restored and Williams clinched a 6-2 4-6 7-5 win.
"The older I get, I think the tougher I get upstairs," Williams told reporters after disappointing the frenzied British crowd to tee up a fourth round clash with sister Venus.
"I think every year, maybe this time next year I'll be probably even stronger."
The astonishing finale to the Centre Court action had shaken up an otherwise routine day at SW19 where Novak Djokovic and Maria Sharapova had imposed their own brutal authority on their battered opponents.
Djokovic dispatched a beleaguered Bernard Tomic 6-3 6-3 6-3 and Sharapova polished off Romanian Irina-Camelia Begu also in straight sets in their third-round matches.
Neither of the defeated duo, however, showed a fraction of the fight on display from 23-year-old Watson.
When Serena hits top gear, her opponents have a habit of rolling over, but the Briton overcame the disappointment of being steamrollered in the first set to rebound in the second, forcing Williams into a string of wild shots.
She reeled off six games in a row to clinch the second set and take a 3-0 lead in the third and served for the match at 5-4 having appeared to tame the Williams fightback.
Twice in the next game she was two points from the match, but Williams took her chances and after engineering a 6-5 lead, the American claimed victory on her third match point to leave Watson reflecting on a positive display but gut-wrenching result.
"I gave myself the opportunity to beat her. I didn't take it this time," she said. "But I'm really glad I was in that situation because I can learn from it."
The other top seeds had a far less testing day.
Djokovic has yet to drop a set and has barely broken sweat in reaching the last 16 and at times in his victory over Tomic his gymnastic defence was at its jaw-dropping and ligament-stretching best.
When the Serb is scrambling from left to right on the baseline and retrieving everything that comes back on to his side of the net, you half expect his battered opponent to throw in the towel.
To Tomic's credit, he scrapped and battled to the bitter end but the 27th seed looked a relieved man to escape from a sun-baked Centre Court when Djokovic, chasing a third Wimbledon title, smacked down his 15th ace to close out the match.
Such was Djokovic's dominance, his opponent might have suspected the world number one of having an extra limb -- and not the prosthetic one he was handed to sign by an eager fan at the end.
"This gentleman gave me his artificial leg and my signature will make him feel better," he quipped, before giving his future opponents a warning as to his current form.
"I was hoping I could play better and better as the tournament progresses and that is what is happening. As we are moving on, I feel more confident."
It was a similarly one-sided story on Court One where Sharapova eased past Begu 6-4 6-3.
There were some picture-perfect backhands on display as fourth-seeded French Open champion Stan Wawrinka's seamless progress continued with a 6-4 6-3 6-4 win over Fernando Verdasco, while Richard Gasquet sent misfiring Bulgarian 11th seed Grigor Dimitrov packing in straight sets.
Australian firebrand Nick Kyrgios reached the next round, beating seventh seed Milos Raonic 5-7 7-5 7-6(3) 6-3 while arguing with one of the crowd and being told to reverse a headband after falling foul of the all-white dress code.
Editing by Ed Osmond and Ken Ferris