"The injury has not completely healed," Bartoli said of the strain suffered during the Wimbledon tournament.
The absence of France's Bartoli, who is ranked seventh in the world, leaves Agnieszka Radwanska (No. 4) as the only player ranked in the top 10 in the world left in the 28-player field.
No. 13 Samantha Stosur, of Australia, is the only other player ranked in the top 20.
Bartoli, who reached the Stanford final three times, was replaced by American Mallory Burdette, who is ranked 78th.
"It is unfortunate she will not be able to attend," said tournament spokeswoman Kim Hall.
The tournament, which includes both singles and doubles players, runs from July 22-28.