AUSTRALIAN OPEN
**Venue: **Melbourne Park ** Date: **18-31 January
BBC coverage:](http://www.paklinks.com/sport2/low/tennis/6102132.stm)Every Murray match live on BBC 1 or 2
Daily from 0830 GMT: live on BBC Red Button/website, 5 Live sports extra
Daily from 0000 GMT: text commentary on BBC Sport website
**Defending champion Rafael Nadal advanced to the fourth round of the Australian Open with a 6-4 6-2 2-6 7-5 win over German Philipp Kohlschreiber.**The second seed’s serve was put under pressure and he needed some inventive shots to win in three-and-a-half hours.
Fourth seed Juan Martin del Potro survived some anxious moments before beating the unseeded Florian Mayer.
The 21-year-old US Open champion served 11 aces but was guilty of 46 unforced errors in a 6-3 0-6 6-4 7-5 victory.
It was another hard-fought victory for the Argentine, who will face Marin Cilic in the fourth round, after the Croatian beat Stanislas Wawrinka of Switzerland 4-6 6-4 6-3 6-3.
Del Potro needed four sets to get past American Michael Russell in the opening round and five to overcome another American James Blake in the second round.
Having beaten Mayer in straight sets in the second round at last year’s Championship, he found him a much tougher proposition this time, and was only 118-117 ahead on total points won.
Mayer took all three of his break point chances to win the second set to love in only 28 minutes before Del Potro clinched the match following two keenly-contested closing sets.
“Especially in the second set, I felt very confused with my game,” he admitted. “But I improved a little bit and in the end I finished the match playing some very good points.”
Giant American John Isner secured a fourth-round match against Britain’s Andy Murray after a gruelling 6-1 4-6 7-6 (7-4) 7-6 (7-5) victory over 12th seed Gael Monfils.
The towering 6ft 9" 24-year-old was given the last seeding for the tournament after Frenchman Gilles Simon withdrew.
It was therefore regarded as a shock defeat on paper, but Isner, who had won two of his three previous matches with Monfils, fired 26 aces and hit 73 winners.
“I was just kind of riding a wave of momentum, and I still am,” he said.
Andy Roddick, four times a semi-finalist in this event, set up a fourth-round tie with 2007 finalist Fernando Gonzalez with a 6-7 (4-7) 6-4 6-4 7-6 (7-3) victory against tenacious Spaniard Feliciano Lopez.
Roddick, who has an 8-3 career advantage over Gonzalez, won in straight sets the last time they met in the round of 16 at the 2008 US Open.
Gonzalez, supported by a throng of exuberant, flag-waving Chilean fans on Show Court Two, beat Evgeny Korolev of Kazakhstan, who likened the experience to being at a football match, 6-7 (5-7), 6-3, 1-6, 6-3, 6-4.
“It was exciting to play in front of this crowd … big support far away from home,” said Gonzalez.