Five-time Grand Slam champion Maria Sharapova withdrew from the WTA Bank of the West Classic just before her scheduled second-round match Wednesday with a left arm injury, tournament officials announced.
"We're sad to announce that @mariasharapova has withdrawn after doctor's advice regarding her left arm," a post on the tournament's Twitter feed said.
Sharapova played her first US match in more than two years on Monday, defeating American Jennifer Brady 6-1, 4-6, 6-0 in an opening-round match at the hardcourt event in Stanford, California.
"Toward the end of the Monday night's match, I felt pain in my left forearm," Sharapova said Wednesday. "After yesterday's scan, the doctor has recommended I don't risk further injury."
The former world number one from Russia hadn't played in the US since March of 2015, before serving a 15-month doping suspension for the use of meldonium.
Seventh-seeded Ukrainian Lesia Tsurenko advanced by walkover as a result of wildcard entrant Sharapova's early exit.
"Unfortunately, I have to withdraw from today's match," Sharapova said. "Monday night's crowd was so special and I wish I could continue playing but I have to make a preventative decision."
Sharapova told supporters after her Monday match that her cheers meant a great deal to her.
"I feel like I just want to hug everyone and say thank you," Sharapova said Monday. "It's my first match in the States in a really long time, and it's the closest thing to home for me."
The latest injury brings into question whether or not Sharapova will be fit in time for the US Open, which starts August 28, as well as for another key tuneup event in Cincinnati in two weeks for which Sharapova has also accepted a wildcard.
Sharapova, 30, returned to competition in April, but her comeback was disrupted by a hip injury that forced her to withdraw from Wimbledon qualifying.
Sharapova's ranking has fallen to 171 in the world.
"I feel like I'm playing catch-up against everyone who has had a head start," Sharapova said after her match. "All that matters is that I keep playing."
Tsurenko next faces American Madison Keys who survived a test from Caroline Dolehide to reach the quarter-finals, rallying from a set down for a 3-6, 6-2, 6-3 win.
The other day session singles match saw No.5 seed Ana Konjuh edge Natalia Vikhlyantseva 6-4, 7-5 to advance to the last eight, where she'll face Garbine Muguruza who cruised past American teenager Kayla Day 6-2, 6-0.
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