The World number one men's tennis player Roger Federer has had to play three sets to reach the Qatar Open semi-finals while number two Rafael Nadal has had an easier ride when his opponent retired injured to put him in the last four.
Federer has survived a scare from 21-year-old Latvian Ernests Gulbis before winning 6-2 4-6 6-4 to progress to the final four where he will face either Russian Nikolai Davydenko or big-serving Croat Ivo Karlovic.
Nadal has 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.
