Serena Williams will regain her world number one ranking after she beat Ekaterina Makarova 6-3 6-2 in the second round of the China Open.

The result, combined with Dinara Safina's defeat yesterday by world number 226 Zhang Shuai - the lowest-ranked player ever to beat a world number one - means Williams will go top again when the new rankings are announced on Monday.

"Obviously I'm happy to be there because I've worked so hard this year to get there. I think I've earned it," said Williams.

Williams has been ranked number one for 72 weeks in her career but surrendered top spot to her Russian rival back in April.

Williams cruised through her match today. But the eighth and ninth seeds were dumped out today, joining Safina and and Williams' sister Venus on the sidelines.

Eighth seed Jelena Jankovic succumbed 4-6 7-5 6-2 to Peng Shuai, of China - and Victoria Azarenka lost out in a marathon three-hour match against Maria Sharapova, who eventually won 6-3 6-7 (5/7) 7-5.

Sharapova said: "I certainly felt like I stepped it up when I needed to."

There were no such dramas for fourth seed Elena Dementieva - who beat Hungarian qualifier Melinda Czink 6-4 6-3 - or her fellow Russian Vera Zvonareva, seeded seventh and cruising past Italy's Francesca Schiavone 6-3 6-0.

There were also wins today for Flavia Pennetta, Marion Bartoli and Maria Jose Martinez Sanchez.

The 12th and 13th seeds also progressed, Agnieszka Radwanska beating Patty Schnyder 6-4 6-1 and Nadia Petrova seeing off Daniela Hantuchova 6-1 2-6 7-5.

In the first round of the men's event, top seed Rafael Nadal was pushed all the way by former Australian Open finalist Marcos Baghdatis but eventually came through for a 6-4 3-6 6-4 win.

In his first outing since losing in the semi-finals of the US Open to Juan Martin del Potro, Nadal was matched stroke for stroke by his Cypriot opponent before gaining the crucial break at 4-4 in the third set.

"I think I didn't play my best tennis," Nadal, who has been suffering from an abdominal strain, told www.atpworldtour.com.

"That's true. But I improved in the third (set) a lot. Especially in the last four games, I played much better.

"The victory is important because for me, he's a very good opponent, and (at) this tournament every opponent is very tough.

"We are playing here the top 45 of the world, so every match is going to be very difficult."

Nadal will next face James Blake, a 6-3 3-6 6-3 winner over Germany's Florian Mayer.

The shock of the day came courtesy of Lukasz Kubot, who beat third seed Andy Roddick 6-2 6-4.

"I'm going to be making obvious statements here, but I didn't play well," said Roddick.

"I was just trying stuff out there, and nothing seemed to be working that well."

There were no such problems for seeds Nikolay Davydenko, Fernando Verdasco and Robin Soderling - who all advanced.

Former champion Marat Safin beat Jose Acasuso, of Argentina, 6-4 6-2 to seal his progression - while there were also wins for Croatia's Ivan Ljubicic and Viktor Troicki, who will next face Novak Djokovic in an all-Serbian second-round clash.