U.S. Open champion Maria Sharapova pulled out of the Kremlin Cup on Friday because of a right foot strain.
The second-seeded Russian had a bye in the first round and beat Eketerina Bychkova in straight sets Wednesday. She had been set to take on Anna Chakvetadze in the quarterfinals on Friday.
"Unfortunately, I will not be able to play today," Sharapova said. "I felt pain in my right hip back in the hotel after my first match here. I couldn't practice and even walk yesterday. I have to pull out. I'm really disappointed but I have no choice."
On her debut at a home event last season, the then top-ranked Sharapova lost to Dinara Safina in the quarterfinals.