In this AP photo by Charles Krupa, Venus and Serena Williams wave to fans after a 6-1, 6-4 loss to Russia's Maria Kirilenko and Nadia Petrova at the U.S. Open.

The Williams sisters, pretty much unbeatable in major doubles’ competitions,  met their match Sunday at the hands of Russian players Maria Kirilenko and  Nadia Petrova. Venus suffers from  Sjögren’s syndrome, an autoimmune disease, and it clearly affects her play at times. I feel awful for her — she tries so hard.

Victoria Azarenka takes on Samantha Stosur, and the stats side with Azarenka, but Stosur is the defending champion. No matter who wins this one – -the road ahead is not easy.

Sara Errani plays  Roberta Vinci, and these two Italians are a doubles team — after they play doubles today, they will face off in singles.  Serena Williams plays Ana Ivanovic, and Maria Sharapova plays Marion Bartoli. That will whittle it all down to a final four.

I’ve seen Errani play and she has beaten some big names. Williams is playing some of her best tennis ever. Maria can always pull off a surprise and no can count out Stosur, Bartoli or Azarenka.

On the mens side, Andy Roddick plays Juan Martin del Potro tonight, and this will be Roddick’s toughest match yet. I have watched a lot of Roddick because every match could be his last.  Novak Djokovic will take on the winner, so we can all hope Roddick has an extra bag of tricks to extend his wins, but the closer we get to the finals, the more I wonder if Roddick has the steam to get there. And  Roger Federer is guaranteed to be well rested because his opponent American Mardy Fish defaulted yesterday due to health problems.

I am loving the coverage — just loving it — you can watch live on http://www.usopen.org/index.html and of course on TV.

Pam Parker has been a tennis player for more than 35 years.  She is the editor of Lake Erie LifeStyle, Her Times and House to Home at the Erie Times-News in Erie, Pa.