Naomi Osaka Pulls Out Of Stuttgart Semis With Injury

World number one Naomi Osaka has pulled out of Saturday's 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 Sunday's final where she will face the Czech Republic's Petra Kvitova.

"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. 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-times 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.

Saturday's other semi-final went the distance as world number three Kvitova beat Kiki Bertens 7-6(3) 3-6 6-1 in an engrossing physical battle that clocked two hours.

Both players exchanged breaks of serve early in the opening set and the pair looked to use every inch of the court and the indoor stadium with one of Kvitova's lobs hitting the roof of the Porsche-Arena to give Bertens the point.

Bertens then saved set points on her serve, preventing Kvitova from breaking her, to take the first set into a tiebreak. But Kvitova controlled proceedings to win the decider.

However, Bertens raised her game in the second set and stormed back into the match with a mixture of powerful baseline shots and delicate chips which had Kvitova scampering around the court to keep up with the Dutchwoman.

Kvitova regained control and broke twice in the final set to take a quick 5-0 lead, putting Bertens on the back foot with deep cross-court shots. The Czech even employed serve-and-volley to take points off her bewildered opponent.

Bertens never recovered and despite successfully serving to stay in the match and getting on the scoreboard, Kvitova served out to win the match and book her place in the final.

"I'm always playing three-setters with Kiki so I didn't expect anything easier today," Kvitova said after she reached her fourth final of the year. "I'm just glad I was able to stay in the rallies and return her serve.

"I really had to be patient and I had to wait for a good shot to go for the winner. Overall, I was pretty good on the legs (to move around the court) today."