AUSTRALIAN OPEN
**Venue: **Melbourne Park ** Date: **18-31 January
BBC coverage:](http://www.paklinks.com/sport2/low/tennis/6102132.stm)Murray v Isner, Sunday midnight GMT: live on BBC One/Online/5 live
**Andy Murray knows he needs his return to be in prime form if he is to come through his fourth-round match against John Isner at the Australian Open.**American Isner, who upset Gael Monfils in the last round, stands 6ft 9ins tall and has served 81 aces so far.
“Playing against someone like him is so dangerous,” said fifth seed Murray, who meets Isner in the first match on Rod Laver arena at midnight GMT on Sunday.
“It might come down to a few points. I’ll have to step up to the plate.”
Isner, 24, hit a career-high ranking of 28 before the tournament began after winning his maiden ATP title in Auckland, a victory which also saw him overtake Sam Querrey as American number two behind Andy Roddick.
He needed five sets to overcome Andreas Seppi in the first round in Melbourne, before seeing off Ireland’s Louk Sorensen and world number 12 Monfils.
“Andy is one of the top favourites for the title I would guess… he might even be the favourite”
Isner on Murray
“He’s very similar to (Ivo) Karlovic,” said Murray.
“None of the guys really enjoy playing against him. He’s a bit better from the back of the court than Karlovic, but Karlovic probably volleys better. It will be a really tough match.”
Isner, though, is also expecting a difficult match against one of the game’s best returners.
“It’s going to be a challenge to hold serve. That’s going to be my number one focus, and taking it from there,” he said.
"Andy’s such a really, really good player. I’m going to have to play really, really well to have a chance out there.
“He’s one of the fittest guys on tour. He really can do anything. He can play offence. He can play defence. He can mix it up really well.”
He added: "He’s one of the top favourites for the title I would guess. Him, Federer, Nadal, Del Potro, Djokovic. Andy might even be the favourite.
“Hopefully I can put an end to his run, but it’s going to be a tough task.”
Murray is looking to break new ground at Melbourne Park with a place in the quarter-finals, where he could come up against world number two Rafael Nadal.
606: DEBATE
“Serve remains a problem for Murray. I think to win he needs to average 65% plus on first serve during the second week”
theweedink
Nadal, though, has a similar task to Murray when he meets Karlovic in a match that immediately follows the Scot’s clash with Isner.
The evening session in Melbourne features Justine Henin against Yanina Wickmayer, and concludes with Roddick’s potentially explosive fourth-round meeting with Fernando Gonzalez.
Juan Martin del Potro’s encounter with Marin Cilic looks set to be the highlight of proceedings on the Hisense Arena.