Murray struggles to tame Melzer in Doha

( Reuters) - World number one Andy Murray laboured past Austrian Gerald Melzer 7-6(6) 7-5 to reach the quarter-finals of the Qatar Open on Wednesday after defending champion Novak Djokovic had also progressed with relative ease.

A passive Murray dropped serve twice in the opening set and world number 68 Melzer saved eight set points with some brave hitting before the Briton took the opener on a tiebreak.

Left-hander Melzer continued to strike the ball heavily, especially off the forehand side, and Murray grew visibly rattled at his inability to polish off his opponent.

Eventually the Scot got the break in the seventh game of the second set but he failed to claim victory when serving at 5-4 as the 26-year-old Melzer forced a break of his own.

When the 29-year-old Murray served for the match for the second time he made no mistake, wrapping up victory when Melzer sent a backhand return wide.

Murray, who looked drained at the end, will play Spain's Nicolas Almagro next.

"He played great, great tennis and dominated large parts of the match," Murray said on court after warmly congratulating his opponent. "I told him at the net he will keep climbing the rankings if he plays tennis like that."

"I played pretty good but he was hitting the ball huge."

Djokovic, seeded two, had an easier time against Argentina's Horacio Zeballos, winning 6-3 6-4 in 72 minutes.

The Serb will face 38-year-old Czech Radek Stepanek who became the oldest ATP Tour quarter-finalist since Jimmy Connors, aged 42, in 1995, when he beat wildcard Arthur De Greef.

(Reporting by Martyn Herman, editing by Neil Robinson)