Clive Brunskill/Getty Images
Sharapova withdrew from the Open on Wednesday due to a shoulder injury.
The tennis star has experienced shoulder injuries before. In 2008 she withdrew from the U.S. Open for the same reason.
Sharapova hasn't had a great couple of months. After losing in the second round of Wimbledon, she has only played one match. Recently she fired her coach Jimmy Connors after only a month.
USTA Executive Director and COO said:
"Maria Sharapova is one of the great warriors of the tennis world. If she withdrew, there's a serious issue."
The U.S. Open tournament, held in Queens, NY, begins Monday.