Venus Williams withdrew in the second game of her third-round match against Andrea Petkovic at the Australian Open on Friday after appearing to aggravate a stomach injury.

The seven-time Grand Slam winner dropped serve in the opening game and Petkovic was ahead 30-0 when Williams stretched to the right to return service. She immediately cried out and clutched her stomach on the right side.

Williams injured a muscle between her stomach and groin Wednesday when she twisted for a volley in her second-round win over Sandra Zahlavova of the Czech Republic. Williams has never before withdrawn due to injury during a Grand Slam match.