John Isner is a big server in every sense of the word. He is 6 feet 9 inches tall, and he routinely rockets a tennis ball at 138 mph. In his three years on the professional tour, Isner has been regarded somewhere between an oddity and the next great American player. Before ousting his fellow American Andy Roddick in a fifth-set tiebreaker and advancing to the fourth round of the U.S. Open last year, Isner had flamed out of his five previous Grand Slam events, failing to get past the opening round. Now he will try to make the quarterfinals of a major for the first time, but he is going to have to go through another Andy to do so: the Scotsman Andy Murray, who is ranked fifth in the world and has yet to lose a set in three matches at the Australian Open. 'Even though he hasn't won a Slam, he's always a guy that's going to be heard from,' said Isner, echoing the sentiment here that Murray is playing well and is talented enough to win the tournament. 'I think that's the same here. Hopefully, I can put an end to his run.' Last week, Isner won his first ATP singles title in Auckland, New Zealand. He is playing perhaps the best tennis of his professional career since turning professional after leading the University of Georgia to the 2007 NCAA team championship. He knows, it, too. 'I've worked hard in the off-season -- I put in the time,' said Isner, a 24-year-old North Carolina native. 'I kind of deserve to be where I am now.' On Friday, Isner served up 26 aces against only three double faults to upset 12th-seeded Gaeel Monfils, 6-1, 4-6, 7-6 (4), 7-6 (5). Isner can also swarm the net with a wingspan that can make him look like a human backboard. Against Monfils, Isner reached the net 53 times and came away with 35 points. Even though this is their first meeting, Murray is fully aware that Isner is dangerous. 'The run he's been on, he's a difficult guy to play against,' Murray said. 'He's the guy that everyone talks about all the time.' Referring to the 6-foot-10 Ivo Karlovic, Murray added: 'You don't want Karlovic or Isner next to your name in the draw, because the match is on the other guy's racket. If he serves well and hits some big shots and returns well, Isner is a really tough guy to beat. I'm going to have to be on my game.' Murray knows he must defuse Isner's rocket serves, a task that he concedes is a, well, tall order. 'I have broken serve a lot so far this tournament against guys that have good serves,' Murray said. 'I'm going to need that in the next match because Isner is playing really well. He won a tournament in Auckland last week and beat Andy Roddick at the U.S. Open. He is 6 feet 9 inches and causes people problems. The guy is so tall and he has possibly the best serve on the tour. I'll have to return well again.' Isner, too, understands that Murray has an array of shots and will not be overpowered easily. 'It's going to be a challenge to hold serve,' Isner said. 'That's going to be my No. 1 focus, first and foremost, is holding serve, and taking it from there. As long as I'm doing that, I know I'll be in the match.' Win or lose, he believes he is heading in the right direction. 'I know that's where my ranking is going, and I'm going to get there,' Isner said. 'If I play my game and I play well, I like to think I can beat anybody.' 