(Reuters) - Women's world No. 1 Naomi Osaka has pulled out of Saturday's (April 27) semi-finals at the Porsche Tennis Grand Prix in Stuttgart after failing to recover from an abdominal injury she suffered in her quarter-final match.
The top seed's withdrawal gives her opponent Anett Kontaveit a walkover and the Estonian goes through to the final where she will face the winner of the other semi-final between Petra Kvitova and Kiki Bertens.
"I'm really sorry I'm not able to compete for the semis today," Osaka said. "I unfortunately got injured yesterday and I was waiting till today to see if I could get better.
"But unfortunately, I didn't... In the morning I had to roll out of bed and couldn't do much. I didn't try to practise, I can't lift my upper body.
" I'm really sorry for everyone that came out and I hope to see you next year and I hope to play next year."
The two-time Grand Slam champion had pulled off an epic comeback from 1-5 down in the final set on Friday when she beat Croatian Donna Vekic 6-3 4-6 7-6(4) despite struggling on the clay surface, making 45 unforced errors.
Osaka said she would stay in Europe and undergo medical examinations to determine whether she has suffered a strain or a tear.
She added she has had abdominal injuries in the past and remained upbeat that she would not be sidelined for too long in the run-up to the French Open Grand Slam, which starts on May 26.
"I am happy it happened in the beginning (of the clay court season) and not in Rome (in mid-May) so close before the French Open," she said, adding on her Stuttgart showing: "I am happy I won two matches. It is a really good boost for me."