 Venus Williams joins her sister Serena on the sidelines |
Venus Williams has withdrawn from the US squad for this weekend's Fed Cup semi-final against Russia because of a knee injury.
Venus, who hurt her knee in Miami last month, joins her sister Serena in sitting out the tie in Alabama.
Captain Mary Joe Fernandez had left a spot open for the world number four.
But Williams said in a statement: "I am continuing to rehabilitate my knee and regret that I will not be able to participate in the Fed Cup tie."
She added: "I waited until this moment in the hope that I would have an opportunity to play but I am being advised by my medical support team that I will need more time to recover.
"I will be rooting for a United States win and look forward to returning to Fed Cup competition."
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Neither Venus nor Serena have played in the Fed Cup since 2007 and Fernandez said: "We're kind of used to not having either Venus or Serena around, so it's not like a shock to the team that really disrupts it."
With the Williams sisters out Fernandez has been forced to rely on a very inexperienced line-up, including Melanie Oudin, Bethanie Mattek-Sands and South African-born Liezel Huber.
Teenagers Sloane Stephens and Julia Boserup travel as back-up in case of further injuries.
Several members of the Russian team have been stranded in Europe by the volcanic ash cloud but are expected to arrive in time for the match.
The other semi-final takes place in Rome, where defending champions Italy will play their first ever Fed Cup tie at the famous Foro Italico - venue for the Italian Open - as they host the Czech Republic.
