Roger Federer has raised concerns over his fitness ahead of the Australian Open after pulling out of the Qatar Open with a back injury.

33231 - Federer pulls out of Qatar with back injury

The world No. 3 revealed he suffered the injury during his second round win over Grega Zemlja on Wednesday, and despite navigating his way past Andreas Seppi in the quarter-finals, the defending champion is still struggling with the problem.

He was due to play Jo-Wilfried Tsonga in Friday's semi-final, but the Frenchman now progresses to the final, where he awaits either Rafael Nadal or compatriot Gael Monfils.

"I hurt my back in the second round and I don't see any improvement today," Federer said. "I've played through two matches in pain and don't think it's the right thing to risk anything more now. It's the only right decision to make.

"I've just been trying to manage the situation really. Back spasms happen and sometimes you can contain them with massage and pain killers. But I don't want to drive myself crazy with more painkillers and I need to do what's right to get it better."

It is only the second time in Federer's career that he has pulled out during a tournament, but despite admitting to being in some discomfort, the 16-time grand slam champion remains confident he will be fit in time for the Australian Open, which begins on January 16.

"It is only the second time I have pulled out from a tournament and I have never pulled out during a match," Federer added. "It's a sad moment for me, the tournament and the fans, but health comes first.

"Although it's not very good, it's not crazy bad. I have had bad backs in the past but this is not very good, otherwise I would definitely be playing. I feel that without play and with the right treatment, I will get through it in the next few days. That's my personal opinion right now.

"Then of course I have a long journey in front of me going to Australia but I hope maybe midweek next week I should be a 100% again. But that's just guessing."