LONDON - Top seed Maria Sharapova survived a scare to reach the Wimbledon third round where she was joined by her biggest rival for the women's title Serena Williams on Thursday.

Andy Murray also gave home fans cause for concern when dropping a set against big-serving Croat Ivo Karlovic in the second round but eased through 7-5 6-7 6-2 7-6 on a sweltering Center Court.

World number one Sharapova, who elected to come off court in the Wednesday night gloom when leading by a set and 3-1 against dangerous grasscourter Tsvetana Pironkova, went into meltdown for a while on the resumption in sticky lunchtime heat on Court One before prevailing 7-6 6-7 6-0.

Williams, the four-times champion who Sharapova beat to win her sole Wimbledon crown in 2004, was far more ruthless in a 6-1 6-4 defeat of Hungarian qualifier Melinda Czink.

After contrasting victories they both ganged up on Frenchman Gilles Simon who ruffled a few feathers with his comments suggesting women players do not deserve equal prize money.

"I'm sure there are a few more people that watch my matches than his," French Open champion Sharapova was quick to point out.

Serena echoed the comments of the Russian. "Oh, my gosh. You know I can't bite my tongue," sixth seed Williams told reporters.

"I mean, definitely a lot more people are watching Maria than Simon. She's way hotter than he is. Women's tennis I think is really awesome."

Serena Williams of the US hits a return to Melinda Czink of Hungary during their women's singles tennis match at the Wimbledon tennis championships in London, June 28, 2012.[Photo/Agencies]

Williams, who has not added to her 13 Grand Slam titles since returning this time last year from a career-threatening foot injury and health problems, was razor sharp as she booked a third-round clash with China's Zheng Jie.

With sunshine and high temperatures replacing the drizzle of the day before which prompted the closure of the Center Court roof, organizers worked through a backlog of postponed and unfinished second-round matches in the top half of both singles draws.

The sudden rise in the mercury was all too much for a few, with one ballgirl taken ill on Court 14 and a spectator fainting while watching Andy Roddick beat Bjorn Phau 6-3 7-6 6-3.

In the bottom half, twice former champion Rafa Nadal was the last match scheduled on Center Court against Czech Lukas Rosol while over on Court One women's champion Petra Kvitova was due to face Briton Elena Baltacha.

Sharapova had saved five set points against the 2010 semifinalist Pironkova on Wednesday before moving into a commanding position, only to pack her bags three games shy of victory.

That decision looked odd at the time and even more so as she made a ragged start on Thursday.

Bulgarian Pironkova, whose serve is a menace, immediately got back on level terms at 3-3 and when the second set reached a tiebreak she went 6-1 ahead. Sharapova fought off a couple of set points before hitting a forehand long.

Pironkova double-faulted on a game point at the start of the third and that proved the spark for Sharapova to catch fire again and rattle off six successive games and set up a meeting with Chinese Taipei's Hsieh Su-wei. Unlike Williams, though, she will not get a rest day and will be back on court on Friday.

Maria Sharapova of Russia reacts during her women's singles tennis match against Tsvetana Pironkova of Bulgaria at the Wimbledon tennis championships in London, June 28, 2012.[Photo/Agencies]

"I started with no motor whatsoever and felt like I was (stuck) on pause," Sharapova, who was clearly not happy with her performance, particularly on serve, told reporters.

"But she is someone who comes out and fires. If she played on grass 365 days a year she would be in the top five."

While all eyes remain on the men's "big four" two of the new generation continued to impress on Thursday as they moved into the third round.

Kei Nishikori, the 19th seed, beat France's Florent Serra 6-3 7-5 6-2 to become the first Japanese male player to reach the third round of the men's singles since Shuzo Matsuoka 17 years ago.

Belgian David Goffin, who gave Roger Federer a big scare at the French Open this month, backed up his impressive first-round win over Australian 20th seed Bernard Tomic with a four-set victory over American Jesse Levine.

The women's seeds flourished in the sunshine with former French Open winners Ana Ivanovic and Francesca Schiavone reaching the third round but former Wimbledon finalist Marion Bartoli fell at the second hurdle to Mirjana Lucic.