LONDON, June 27 (Reuters) - It took less than two brutal hours at Wimbledon on Monday to disprove the theory that Serena and Venus Williams could march back to continue their domination of the grasscourt slam having hardly swung their rackets in anger for months.
First defending champion Serena was bundled out in the fourth round 6-3 7-6 by livewire Frenchwoman Marion Bartoli then five-times champion Venus was destroyed 6-2 6-3 by Bulgarian Tsvetana Pironkova.
World number one Caroline Wozniacki also departed but the Manic Monday carnage did not extend to the men's singles although defending champion Rafa Nadal suffered a major injury scare during a scintillating late evening win over Juan Martin del Potro in front of a captivated Centre Court crowd.
Nadal won 7-6 3-6 7-6 6-4 while six-times champion Roger Federer lost his first set of the tournament in beating Russian Mikhail Youzhny as home flag bearer Andy Murray and world number two Novak Djokovic sauntered through in straight sets.
Nadal needed lengthy treatment on a mystery foot complaint at 6-6 in the first set and admitted he feared at the time his title defence was over.
"It felt terrible at 6-5," Nadal, who extended his Wimbledon winning streak to 18 matches, told reporters. "It felt like I had broken my foot, I didn't know if I could continue playing."
The 25-year-old will have an MRI scan to assess the damage.
Australian Bernard Tomic continued his memorable run, the 18-year-old thrashing Belgium's Xavier Malisse to become the youngest player to reach the men's quarter-finals since 1986.
Wozniacki's shock 1-6 7-6 7-5 loss to Slovakia's Dominika Cibulkova came in the immediate aftermath of the double Williams bombshell and left 2004 champion Maria Sharapova as the clear favourite for the title after the Russian fifth seed overpowered China's Peng Shuai 6-4 6-2.
Serena, who returned from 11 months out with a lacerated foot and then life-threatening blood clots just in time for Wimbledon, spent the first three rounds shaking off the rust and appeared to be rediscovering the firepower that has brought the 29-year-old 13 grand slam titles.
Once again she scrapped like an alley-cat but the unorthodox Bartoli, beaten by Venus in the 2007 final, proved a match too far for the champion whose hopes of three consecutive titles evaporated in oppressive heat on Court One.
After defeat, though, she fired out an ominous warning to her rivals and anyone preparing to write her off.
"Even today I lost, but I was able to kind of hang in there and play tough," Williams, who was watched by friend and soul diva Beyonce, told reporters. "And I can only get better. And that can potentially be really scary, because I can only go up from here and I can just do so much more."
Bartoli appeared to be playing with fire at times, jumping around inside the baseline as her opponent wound up her mighty serve and fist-pumping towards Williams after big points.
She carried it off, though, claiming her first victory over the American on her fifth match point after some fidgety moments for father and coach Walter, who Bartoli had banished from court on Saturday.
While Serena at least went down fighting, 31-year-old Venus produced a lame performance against Pironkova, the player who stopped her in the quarter-finals last year.
"Unfortunately I seem not to have my good days against her," Venus said. "I think we both envisioned seeing this day going a little bit different."
Bartoli will take on Sabine Lisicki on Tuesday after the German wildcard beat Petra Cetkovska while Pironkova faces Czech Petra Kvitova, also a semi-finalist last year, after she clubbed Yanina Wickmayer 6-0 6-2.
With Sharapova up against Cibulkova and Belarussian fourth seed Victoria Azarenka playing surprise Austrian Tamira Paszek, the quarter-final lineup is an all-European affair for the first time since 1913.
With all eight men's and women's last-16 matches slated on the schedule the All England Club was abuzz from the moments the gates swung open on a stifling morning.
The recently married Prince William and the Duchess of Cambridge had the best seats in the house and would have given their seal of approval to Murray's most impressive display this year as he dismantled Gasquet in three sets.
Next in the number four seed's firing line as he aims to become the first British man to win Wimbledon since 1936 is Spanish left-hander Feliciano Lopez, who hit back from two sets down to beat Poland's Lukasz Kubot.
Nadal's injury woes returned at the end of a high-quality first set when the Spaniard grimaced in discomfort with something clearly wrong with his foot.
After nearly 10 minutes of treatment, Nadal then went 3-0 down in the tiebreak but he fought back to take the opener when an irritated Del Potro double-faulted.
Del Potro unleashed a barrage of forehands to batter Nadal into submission in the second set and when the third went to a tiebreak, the crowd sensed the outcome of it would be crucial.
So it proved as Nadal, scampering about and conjuring astonishing angles, took it and then broke for the first time in the fifth game of the fourth set to subdue the 24th seed and book a last-eight slot against last American standing Mardy Fish, an easy winner against 2010 runner-up Tomas Berdych.
Djokovic, who can replace Nadal as world number one by reaching the final, had a relatively stress-free workout against Michael Llodra, dropping just nine games en route to an intriguing quarter-final with young gun Tomic.
Third seed Federer had a jolt when he lost an opening set tiebreak to Youzhny but was majestic thereafter, gliding through the next three sets 6-3 6-3 6-3.
Next up for Federer is charismatic Frenchman Jo-Wilfried Tsonga, who reached the quarter-final for the second year in a row with a 6-3 6-4 7-6 win against Spain's David Ferrer. (Reporting by Martyn Herman)