Nadal stands test of knees in round two

Ferrer retires hurt in the battle of Spaniards

Sidelined for more than two months with tendonitis in both knees, Nadal's tender joints were in the spotlight for his first singles match since his shock loss to Sweden's Robin Soderling in the fourth round of the French Open in May.

But it was Ferrer's left knee that became the talking point after he abruptly retired when trailing 4-3 in the opening set.

Having betrayed little sign of discomfort, Ferrer's withdrawal prompted gasps and groans from the centre court crowd.

Ferrer's retirement whisked Nadal into a third-round meeting with Philipp Petzschner of Germany. Resurgent Spaniard Juan Carlos Ferrero defeated 13th seed Gael Monfils of France 6-3, 7-6 to move into the third round. American fifth seed Andy Roddick also advanced with a tidy 6-1, 7-6 win over Russian Igor Andreev. Sixth-seeded Juan Martin Del Porto of Argentina defeated Czech Jan Hernych 6-2, 7-5, while seventh seed Jo-Wilfried Tsonga of France survived a scare to beat over Germany's Rainer Schuettler 4-6, 6-3, 6-4.

Spanish 10th seed Fernando Verdasco raced into the third round with a 6-1, 6-1 demolition of Argentina's Leonardo Mayer.

Third seeds Mahesh Bhupathi and Mark Knowles edged past Jeff Coetzee and Jurgen Melzer 7-6 (7-2), 6-4 to book a quarterfinal berth.

Clijsters advances
Kim Clijsters's comeback gathered pace on Wednesday when the former world number one beat Swiss Patty Schnyder 6-2, 7-5 to reach the third round of the Cincinnati Open.

Second seed Serena Williams also advanced to the third round after overpowering Kateryna Bondarenko of Ukraine 6-3, 6-2.

Fourth seed Elena Dementieva saw off Belgian qualifier Yanina Wickmayer 6-3, 6-4 while fifth seed Jelena Jankovic advanced with a 7-6, 6-3 victory over Russian Maria Kirilenko Jankovic's next opponent will be ninth seed Victoria Azarenka of Belarus, a 6-4, 6-2 winner over Anna Chakvetadze of Russia. Italian Flavia Pennetta secured a meeting with third seed Venus Williams by beating Hungary's Agnes Szavay 6-2, 6-4, extending her winning streak to 13 matches.

Seventh seed Vera Zvonareva survived a second-set blip to oust Russian Alisa Kleybanova 6-4, 1-6, 7-5 but former world number one Ana Ivanovic of Serbia was upset 7-6, 7-5 by Hungary's Melinda Czink.

Sania, Schiavone exit
Sania Mirza and her Italian partner Francesca Schiavone crashed out of the doubles event following a straight set 4-6, 3-6 defeat against top seeds Cara Black and Lizel Huber.