Britain's Andy Murray set up a semi-final clash with Roger Federer after a comfortable 6-4 6-2 win over Ukraine's Sergiy Stakhovsky in the Qatar Open.
Stakhovsky posed the defending champion problems until fatigue seemed to set in towards the end of the first set.
World number two Federer beat Germany's Philipp Kohlschreiber 6-2 7-6 (8-6).
Earlier, world number one Rafael Nadal suffered a straight sets defeat to France's Gael Monfils and afterwards blamed a lack of match practice.
The fifth-seeded Monfils had never won a set in three previous meetings with Nadal, but dominated from the start to cruise home 6-4 6-4 and make the semi-finals.
"He played better than me. That's what happened," said Spain's Nadal. "I had my chances but he was serving really well. Maybe I need more time on court.
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"I played two matches in Abu Dhabi and three here, which is good, but I need more matches.
"There is still 1½ weeks to go for the Australian Open. I am not playing any event anywhere now.
"I will practise here and I fly out to Australia on Sunday. I will not go with any bad feeling with this loss. I am playing well. I just need more matches."
Andy Roddick easily beat Victor Hanescu 6-3 6-2 and will next play the Frenchman on Friday.
However, all British eyes will be on the mouth-watering semi-final between Murray and Federer.
It will be the seventh meeting between the two men and although Murray was far from his best against Stakhovsky, the in-form Scot will be quietly confident of recording a fifth victory over the Swiss star.
Murray said: "I am happy with the way I am playing now. I don't see any reason to doubt my chances in the semi-final either."
After breaking the Ukrainian in the third game, some sloppy play from Murray, who had been leading 40-0 in the fourth, allowed the world number 91 to level immediately.
Stakhovsky, 23, seemed comfortable until Murray, warned during the seventh game for illegal coaching, added some aggression to his play to break for a second time and then hold for the set.
Murray was in complete control of the second set, strolling 5-0 ahead until Stakhovsky got on the board with his second break of the match.
Stakhovsky then saved a match point to make it 2-5, but he was only delaying the inevitable as Murray made no mistake on his second match point.
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