Andy Murray had to earn his place in the quarter-finals of the Qatar Open after a difficult 7-6 (8-6) 7-5 victory over Austria's Gerald Melzer.
It was the first ever meeting between the 29-year-old and the hard-hitting left-hander but the newly-knighted Scot ensured he had a winning start to his head-to-head record in a difficult match against the World No.68, which took a gruelling two hours and 23 minutes to complete.
The duo shared four breaks of serve in an opening set that was taken to a tie-breaker by Melzer and who fought back from 5-0 down to 6-6 in the first-set decider.
The second set was just as frustrating for the World No.1 despite him hitting 10 aces and seeing 78 per cent of his first serves in - but he edged past the 26-year-old to set up a meeting against Spaniard Nicolas Almagro.
Almagro, the World No.44, sealed his place in the last eight with a 7-6 (7-5) 7-6 (8-6) straight-sets success over Germany's Philipp Kohlschreiber.
World No.2 Novak Djokovic eased into the next phase with a 6-3 6-4 victory over Argentina's Horacio Zeballos in just one hour and 13 minutes.
Fernando Verdasco defeated fourth seed David Goffin to advance to the quarter-finals in Doha with a 6-1 7-6 (8-6) win over the Belgian, while the evergreen Radek Stepanek was a 6-3 6-2 victor over Arthur de Greef.
Third seed Tomas Berdych won the battle of the Czechs as he triumphed over compatriot Jiri Vesely 7-6 (7-5) 1-6 6-1, while big-serving Ivo Karlovic defeated Karen Khachanov 7-6 (7-3) 7-6 (7-3).
Berdych will now face fifth seed Jo-Wilfried Tsonga after the Frenchman needed just 45 minutes to breeze past Germany's Dustin Brown in a 6-1 6-3 triumph.
Meanwhile, Britain's Kyle Edmund will face World No.4 Stan Wawrinka in the quarter-finals of the Brisbane International after both came through their second round matches yesterday.
Edmund progressed when opponent Lucas Pouille retired trailing the Briton 6-3 3-1 while second seed Wawrinka beat Viktor Troicki 7-6 (7-5) 6-4.
Third seed Kei Nishikori booked his place in the last eight after coming from a set down to beat qualifier Jared Donaldson 4-6 6-4 6-3.
But eighth seed David Ferrer crashed out of the event following a 4-6 7-5 7-5 defeat at the hands of Australian Jordan Thompson.
In the Aircel Chennai Open, No.1 seed Marin Cilic fell to a second-round defeat to World No.117 Jozef Kovalik by a 7-6 (7-5) 5-7 7-5 scoreline.
Both men earned two breaks apiece during the match but the 24-year-old Slovak used his timely second to his advantage in the decider to serve out one of his biggest victories in his career so far.
Third seed Albert Ramos Vinolas needed just over an hour as he dropped just two games in his comfortable 6-2 6-0 success over Belgium's Steve Darcis.
Israel's Dudi Sela produced a routine 6-2 6-2 win over South Korea's Chung Hyeon while Russian Daniil Medvedev won 6-4 6-3 against Yen-Hsun Lu of Taiwan.