Roger Federer's hopes of a fourth successive ATP title came to a premature end when he withdrew from the Qatar Open with a bad back.
The back spasms Federer felt during matches with Greg Zemlja and Andreas Seppi have not gone away despite treatment and painkillers, and he now feels the risk of compensatory injuries is too great.
He has pulled out to give himself the best chance of appearing in good shape at the first Grand Slam tournament of the year, the Australian Open, starting at Melbourne in ten days time.
Federer was due to have met France's Jo-Wilfried Tsonga, the number three seed, in the semi-finals.
It means that Tsonga, the world number six who wants to break into the top four for the first time this year, goes through for his 13th ATP World Tour final.
He lost to Federer in last year's semis here and now will go one stage further - a final against either Rafael Nadal, the French Open champion, or his fellow Frenchman Gael Monfils.
