Federer survives a scare in Qatar

World number one Roger Federer had to play three sets to reach the Qatar Open semi-finals on Thursday, while number two Rafael Nadal had an easier ride when his opponent retired injured to put him in the last four.

Swiss Federer survived a scare from 21-year-old Latvian Ernests Gulbis before winning 6-2, 4-6, 6-4 to progress to the next round where he will face Russian third seed Nikolay Davydenko who beat big-serving Croat Ivo Karlovic 7-6, 7-6.

"I'm happy to have come through a tough outing. It was pretty hard towards the end. It looked more like Gulbis gave up rather than me earning the victory," Federer told a news conference.

"It's pretty cold out there. That affected my game to some extent and, at times, I just couldn't get going."

Nadal stayed on course for a showdown with the Swiss in the final when Belgium's Steve Darcis retired with an injured back when the Spaniard was leading 6-1 2-0 in their quarter-final.

Nadal will next play Serbia's Viktor Troicki who overcame Poland's Lukasz Kubot 4-6, 6-4, 7-6.

"This wasn't the way I wanted to reach the semi-finals. I feel sorry for Darcis and wish him a speedy recovery. I hope he plays in the Australian Open (January 18-31). When you know you aren't well, it's better to stop," said Nadal.

The Spaniard, however, was happy to be in the semi-finals without dropping a set and said he was back to his best after being plagued by knee and stomach injuries during 2009.

"When I was out of action, I was watching a lot of videos of top players to stay tuned to the game. I'm now ready to win as many tournaments as possible," he said.

"Last month, I had a shoulder problem, but I believe I'm back to my best. I may not serve as fast as Roger (Federer) or Robin (Soderling), but if I can serve between 190 and 200 kph, that'll be fine."