By Martyn Herman

LONDON (Reuters) - The mercury was rising at Wimbledon on Saturday as the serial trophy hunters gathered in the last 16 with defending champions Rafa Nadal and Serena Williams leading the charge and Roger Federer and Novak Djokovic not far behind.

Australian qualifier Bernard Tomic added a new face to the second week of a grand slam when he produced the biggest shock of the men's tournament by beating Swedish fifth seed Robin Soderling in straight sets.

Nadal was in miserly mood as he finished off Luxembourg's Gilles Muller 7-6 7-6 6-0 on Number One court.

Williams, seeded seventh after her return from 11 months of serious health problems, made her most emphatic statement yet by blasting Russia's Maria Kirilenko 6-3 6-2.

"I was a little more consistent and I played my game more," she said. "Wasn't as tight and nervous and uptight. I was able to relax more today," the 13-times grand slam champion.

Maria Sharapova, the 2004 winner, took her customary place at the business end of a major as the fifth seed overpowered Czech Klara Zakopalova 6-2 6-3 on Court Two.

The scheduling of the top women's players on what is the club's third court has been a bone of contention this week after Serena Williams, five-times winner Venus Williams and world number one Caroline Wozniacki have all made their way through the walkways to the sunken bowl.

Wozniacki, still waiting to join the elite club of grand slam champions, enjoyed her upgrade on Center Court for an easy win over 27th seed Jarmila Gajdosova.

She then made way for the club's most decorated member to strut his stuff in the sunshine.

The most absorbing action was saved to last, however, as Djokovic and smiling Cypriot Marcos Baghdatis produced a prime-time sizzler that had Center Court fans roaring their approval.

Djokovic won 6-4 4-6 6-3 6-4 in a match full of sensational rallies and one of the best racket demolitions seen on the famous arena as the Serb second seed vented his frustration in the second set.

"Playing here last five years there were not many moments when I saw practically all the stadium on their feet. It was incredible."

After a stop-start tournament so far, the 125th championships are now simmering nicely with all the ingredients in place for a tasty second week.

"Monday will be kind of cool when all the men play at the same time," said 29-year-old third seed Federer, who faces Russian Mikhail Youzhny.

Nadal returned to Court One a set up after rain stopped play on Friday and after more dogged resistance from wildcard Muller, the last man to beat him at Wimbledon other than Federer, Nadal roared through.

"Seems like the best players are all playing well," the 25-year-old told reporters. "I don't know if I gonna win my next round. Probably the rest of the players thinks the same.


Nadal, who committed just three unforced errors against Muller and is yet to drop a set, had reason for caution as his last 16 opponent is 2009 U.S. champion Juan Martin del Potro who beat Frenchman Gilles Simon.

"I'm not lucky to play against Del Potro in the round of 16," he added. "But that's what it is, and I have to be playing my best tennis to try to win."

Left-hander Muller was still very much a threat until 5-5 in the second-set tiebreak when one lapse was seized upon ruthlessly by the 25-year-old Mallorcan.

"The third set, two sets to love, I am able to play with less pressure," Nadal said. "I started to return unbelievable and to play at very high level."

Tomic, the youngest player in the men's draw who is poised to end Lleyton Hewitt's 11-year reign as Australian number one, won the first four games and twice French Open runner-up Soderling crumbled to a 6-1 6-4 7-5 defeat.

Sixth seed Tomas Berdych, the man Nadal beat to claim his second Wimbledon crown last year, is also looking a threat again after an easy third-round win over Alex Bogomolov Jr., a result that left Mardy Fish as the sole American male survivor.

"It's lonely. It doesn't feel great. And that's not the goal," 10th seed Fish, who faces Berdych next, said.

(Editing by Ed Osmond)