| Federer has been struggling with muscle spasm since the second round of the Qatar Open [EPA]
Defending champion Roger Federer pulled out of his Qatar Open semifinal against Jo-Wilfried Tsonga because of a back muscle spasm on Friday but expects to be fit for the Australian Open.
In a news conference before his scheduled match, the 16-time Grand Slam champion said his back had not improved since beating Andreas Seppi in three sets on Thursday.
Federer, who was looking for his fourth title in Doha, apologised to organisers but said he didn't want to risk further injury ahead of the Australian Open.
It is only the second time the 30-year-old Swiss has pulled out of a tournament due to injury in his illustrious career. The first was at the 2008 Paris Masters, where he withdrew from a quarterfinal also due to a back injury, the ATP said.
"I don't feel a whole lot of improvement for today, and I just don't think it's the right time to risk anything more right now,'' Federer said.
"I still have pain, and that's why it was the only right decision, a difficult one for me... so it's a sad moment for me and for the tournament and for the fans, but health goes first."
Federer said he has tried several treatments including massage and baths after he first felt the injury during his second-round match against qualifier Grega Zemlja.
He played against Seppi but struggled to a three-set victory, trailing 5-1 during the second set and looking out of sorts.
But afterward, he said nothing about the injury.
"For Australia, I'm optimistic, just because it's not very good but it isn't crazy bad"
"It came throughout two points against Zemlja in the beginning, 2-1 in the first set, and then I wasn't able to serve properly anymore,'' Federer said.
"Had the same thing yesterday. I was really playing, you know, with the hand brake on, and I was just trying to manage the situation, really. So it wasn't very easy to deal with.''
Federer said he plans to fly out of Doha on Saturday as scheduled and is hopeful he will recover with rest and further treatment by the end of the week.
"For Australia, I'm optimistic, just because it's not very good but it isn't crazy bad,'' Federer said.
Federer has been one of the few players on tour not to be slowed significantly by injuries over the years and his fitness has been one of the factors in his longevity. There was a time when he played only an exhibition in Melbourne before the Australian Open but he now plays an exhibition in Abu Dhabi at the end of the year and then the Qatar Open before heading to Australia.
The sixth-ranked Tsonga said he was "sad" to hear of Federer's withdrawal as he was relishing the chance to face the guy he lost to six times last year but beat in an epic five-set match at Wimbledon.
"It's good for me to play against him to see how is my level, how I feel, at the beginning of the season against a guy like this,'' said Tsonga.
"I'm sad for him. I'm sad because I will not play."
Tsonga will play either Rafael Nadal or Gael Monfils in Saturday's final.