Naomi Osaka has withdrawn from the Stuttgart Open ahead of her semi-final against Anett Kontaveit due to an abdominal injury.

Osaka produced a rousing fightback to beat Donna Vekic in the quarter-finals on Friday, but she will not end the week by featuring in her maiden clay-court final on the WTA Tour.

Kontaveit will take on either Petra Kvitova or Kiki Bertens in the decider on Sunday.

US Open and Australian Open champion Osaka hit back at her critics after coming from 5-1 down in the final set to defeat Vekic.

"I don't understand why people are saying I'm having a bad season if I won [the] Australian Open, right?" said the 21-year-old.

"Last year, I didn't win [the] Australian Open. Sure, I didn't win Indian Wells [this season], but I still thought I did pretty good there and in Miami, and then I'm here now. 

"So, sometimes I hear people say, Naomi is kind of struggling there, and I'm like yo...."

She added: "I would be lying if I said it wasn't bothering me. I tend to internalise everything, so it just builds up. I think you could tell because I started getting really antsy on court compared to before. If I would make a mistake, I would react upon it. I feel that people that were really watching could tell. 

"I felt I wasn't really enjoying myself. Like for me, when I play my best it’s when I have fun playing tennis and waking up every day with a new challenge. But during those few weeks, I felt like I was waking up wanting to win. I don't think that’s a really good combo."