- Roger Federer withdraws from Qatar Open with back injury
- Three-time defending champion was due to play Jo-Wilfried Tsonga in the semifinals
- Top seed Rafael Nadal facing France's Gael Monfils in second semifinal
- Andy Murray sweeps into semifinals of Brisbane International
(CNN) -- 16-time grand slam champion Roger Federer pulled out of his defense of the Qatar Open Friday with a back injury.
Federer, the three-time defending champion at the season-opening tournament, was due to face France's jo-Wilfried Tsonga for a place in the final.
The Swiss maestro had nursed back spasms during his wins over Greg Zemlja and Andreas Seppi and undergone treatment between matches as well as taking painkillers.
But with the Australian Open looming on Monday week, the World No.3 decided against risking the injury against Tsonga.
"I hurt my back in my second round match (against Zemlja) and I don't see any improvement today," he told gathered reporters.
"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.
"It's only the second time I have pulled out from a tournament, and I have never pulled out during a match. It's a sad moment for me, the tournament, and the fans, but health comes first."
Federer sounded a cautious note ahead of the first grand slam of the season.
"Although it's not very good it's not crazy bad," he said.
"I have had bad backs on the past, but this is not very good, otherwise I would definitely be playing," added Federer, who is on a 20-match unbeaten run on the ATP Tour.
Tsonga will now go into his 13th career final, facing either World No.2 Rafael Nadal or fellow Frenchman Gael Monfils.
Earlier, Andy Murray raced into the semifinals of the Brisbane International with a straight sets win over Marcos Baghdatis of Cyprus.
World No.4 Murray beat Baghdatis 6-2 6-2 and will play Australian hopeful Bernard Tomic for a place in the final in Queensland.
19-year-old Tomic beat Uzbekistan's Denis Istomin 6-3 7-6 in their quarterfinal match.
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