Williams, seeking her sixth Wimbledon title, led 6-1, love-1 when Ivanovic called it quits.
The Williams sisters remained on course for a rematch of last year’s all-family final, which Venus won. No. 2-seeded Serena Williams, seeking her third Wimbledon title, advanced by beating Daniela Hantuchova 6-3, 6-1.
Ivanovic said she hurt her thigh hitting an ace to erase a break point in the opening game of the second set.
“I didn’t feel anything up until that point,” she said. “When I landed, I just felt a sharp pain on my inner thigh, and I couldn’t step on my leg ever since.”
Ivanovic took a 10-minute break during the first game of the second set to have her left thigh taped by a trainer. She returned for two more points, but after hitting a service winner to take the game, she began crying as she walked to her chair and told the umpire she was retiring.
Then she hugged a sympathetic Williams.
“I don’t even know the last time that I had these circumstances,” Williams said. “I don’t think ever in a Slam. I think she was in a lot of pain. You know me — I’m one of those players, I just only pay attention to what’s going on my side of the net. But today I felt really sad for her actually. She was really upset.
“This is Wimbledon. It’s the last place you want to have an injury that you can’t overcome. So I’m wishing her a lot of luck in her recovery.”
Ivanovic said she didn’t yet know the extent of the injury. She hasn’t reached a Grand Slam quarterfinal since winning the 2008 French Open and briefly claiming the No. 1 ranking.
