Russian third seed Maria Sharapova withdrew from the US Open on Sunday with a right leg injury, easing the path to a calendar-year grand slam for top-ranked Serena Williams.

US Open tournament director David Brewer announced Sharapova's exit, which allowed qualifying lucky loser Daria Kasatkina of Russia into the draw in Sharapova's place.

"Unfortunately I will not be able to compete in this years US Open," Sharapova said in a Twitter posting. "I have done everything possible to be ready but it was just not enough time.