On a day when nine Grand Slam singles champions are in action, 16-time major titlist Roger Federer and three-time major winner Maria Sharapova headline night matches on Center Court.

 

Federer, who defeated currently top-ranked American Mardy Fish in last year’s Cincinnati final, plays the night’s second match on Center Court. He’ll meet Juan Martin del Potro in a rematch of the ’09 US Open final, which the Argentine won in five sets.

 

In their six career meetings, Federer leads with four wins, while del Potro has won the last two matches. "I thought both matches were really good. They were both very close," said Federer, who lost the second match at the 2009 Barclays ATP World Tour Finals.

 

"And then [at] the US Open obviously having all the chances…it was a tough one to lose, definitely one of the bigger losses in my career," he continued.

 

Sharapova, who kicks off night action first, faces Anastasia Rodionova in their second round match. The Russian, who lost to four-time Grand Slam champion Kim Clijsters in last year’s three-set Cincinnati final, is seeded No. 4.

 

Coming off a runner-up performance at Wimbledon and a semifinal showing at the French Open earlier this year, Sharapova appears in the same section of the draw as 2011 French Open champion Na Li of China.

 

Three-time Tour titlist Rodionova qualified to get into the main draw, defeating 2011 Bastad winner Polona Hercog in the first round 6-0, 6-0.

 

In their career head-to-head, Sharapova has won all three matches with the most recent coming at the ’07 Australian Open second round.

 

James Blake, the Cincinnati finalist in ’07 and doubles titlist in ’02 with Todd Martin, takes on 2011 French Open quarterfinalist Fabio Fognini on the Grandstand. The Italian upset 14th-seeded Viktor Troicki 6-4, 6-1.

 

On Court 3, 2011 Wimbledon champion Petra Kvitova faces Russia's Chanelle Scheepers, who upset World No. 39 Rebecca Marino of Canada in the first round.