Murray battles on after another sluggish start

If Andy Murray carries on like this, his supporters will be nervous wrecks before the first month of the season is over. For the second match in succession, the 24-year-old Scot lost the opening set in his first tournament of the year before beating Luxembourg's Gilles Muller 4-6, 7-6, 6-0 to claim his place in the quarter-finals of the Brisbane International.

Having faced two break points to go 5-3 down in the second set, Murray went even closer to defeat than he had against Mikhail Kukushkin 24 hours earlier, but once again the world No 4 improved rapidly in the closing stages to seal victory. Murray will play Marcos Baghdatis in the quarter-finals tomorrow. He was due to appear on the same side of the net as the Cypriot today against Jurgen Melzer and Philipp Petzschner in the doubles.

Murray was playing in a bright orange shirt and blue shorts, but his tennis at the end of the first set was lacklustre. Having appeared in little trouble, the Scot handed Muller the advantage by playing four poor points in succession when he served at 4-5.

The match turned when Murray took control of the tie-break, in which he created four set points by winning a superb rally, chasing down a drop shot and then racing back to retrieve a ball struck deep to his backhand. Muller won only seven points in the final set before Murray completed victory after exactly two hours when the world No 54 hit a forehand beyond the baseline.

Murray admitted that it had taken him time to cope with Muller's big serve, though he always felt confident whenever he got into the rallies. The Scot, who wore strapping on his right knee, again looked to be in some discomfort but insisted that "it becomes easier with each match". He added: "I moved better in the second and third sets and that's such a big part of my game."

Earlier in the day, Serena Williams had physical problems despite recording a 6-2, 6-4 victory over Serbia's Bojana Jovanovski. The American, who was playing in her first tournament for four months, sprained an ankle and later withdrew from the tournament. She still hopes to be fit for the Australian Open, which begins in 11 days' time.

Rafael Nadal, whose start to the year has been hampered by a shoulder injury, showed improved form to beat Germany's Denis Gremelmayr 6-2, 6-2 and reach the quarter-finals of the Qatar Open in Doha. Roger Federer needed only an hour to beat Slovenia's Grega Zemlja 6-2, 6-3, while Jo-Wilfried Tsonga, the No 3 seed, beat Italy's Flavio Cipolla 7-6, 6-3.

Elena Baltacha, the British No 1, who had won her opening match in Auckland, was beaten 6-4, 6-2 by Flavia Pennetta in the second round. The first set was tight, with just one break point apiece, but while the Italian converted hers Baltacha was unable to do the same.