Melanie Oudin will replace Sloane Stephens on the United States Fed Cup team for a first-round tie in Italy this week.
The rising 19-year-old Stephens suffered an abdominal strain during her run into the Australian Open semifinals last month.
"I'm terribly disappointed that I won't be able to play for my country in Italy," said Stephens, who is ranked a career-high No. 17 in the WTA rankings and is 10-3 this year. "I played a lot more matches than I expected in four straight weeks in Australia and need to be careful not to let this ab injury sideline me for a long time."
The 21-year-old Oudin joins Fed Cup rookies Varvara Lepchenko and Jamie Hampton, as well as doubles stalwart Liezel Huber. The Americans were already heading to Rimini without the services of the Williams sisters -- former world No. 1s Serena and Venus.
Team USA is captained by fifth-year skipper Mary Joe Fernandez.
The United States leads all nations with 17 Fed Cup titles, but hasn't captured the chalice since 2000.
The USA-Italy winner will face the Australia-Czech Republic victor in a semifinal in April.