Serena Williams is the latest player to pull out of the Fed Cup semi-final between the USA and Russia in Vermont.
The Australian Open champion, who reached Wimbledon’s quarter-finals, is still recovering from a hand injury and has been struggling with a calf strain.
Meilen Tu, the world’s 41st ranked player, will replace the 25-year-old when the tie begins on Saturday.
Russia, who lost Maria Sharapova to injury on Tuesday, saw Svetlana Kuznetsova pull out on Thursday.
“I’ve talked to (Serena) and I’ve also gotten an e-mail,” said US captain Zina Garrison. “She wasn’t very happy that she wasn’t able to come.
“The doctors advised her, for this week, it wouldn’t be a good idea to risk possibly straining her thumb a little bit more.”
Russian skipper Shamil Tarpishchev, who only obtained a US visa on Thursday, named Nadia Petrova, Anna Chakvetadze, Yelena Vesnina and Alla Kudryavtseva in his squad.
Tu joins Venus Williams, doubles specialist Lisa Raymond and Vania King in the US line-up.
The other semi-final sees defending champions Italy host France on clay in Castellaneta.
France travel with Amelie Mauresmo, Tatiana Golovin, Nathalie Dechy and Severine Bremond, after captain Georges Goven turned Wimbledon runner-up Marion Bartoli’s request to be accompanied by her father and coach, Walter.
Francesca Schiavone, Mara Santangelo, Tathiana Garbin and Roberta Vinci carry Italy’s hopes.