Serena Williams is pulling out of the US' Fed Cup semi-final against Russia this weekend because she injured herself during Wimbledon, a source at the US Tennis Association said on Wednesday.
The eight-time Grand Slam singles champion will be replaced by Meilen Tu, who flew to Stowe, Vermont on Wednesday to join the rest of the squad.
The source spoke on condition of anonymity because Williams' withdrawal and replacement by Tu were not going to be announced formally until yesterday. The draw for the best-of-five semi-final happens today, with the matches over the weekend.
Williams and her older sister Venus were part of the four-player team announced last month by US captain Zina Garrison, along with doubles specialist Lisa Raymond and teenager Vania King. But five days later, Serena Williams strained her left calf and hurt her left wrist and thumb during her fourth-round victory on the grass at Wimbledon.
Particularly hampered by the wrist and thumb -- she had to hit backhands with one hand instead of two -- she lost to Justine Henin in the quarter-finals at the All England Club. On Tuesday, Williams pulled out of next week's WTA tournament in Mason, Ohio.
She and Venus, who won Wimbledon for her sixth major title, were on the US team that beat Belgium 5-0 in the Fed Cup quarter-finals at Delray Beach, Florida in April. That was Serena Williams' first Fed Cup action since 2003, and Garrison has spoken about the sisters' commitment to participate in the competition and win it -- if healthy.
The US hasn't won the Fed Cup title since 2000.
The 41st-ranked Tu complained last month that she hadn't heard at all from Garrison before the team was picked.