Rafael Nadal again had to brave stormy weather on his way to victory at the Australian Open yesterday, but the Spaniard is well aware that the hard times are only just beginning if he is to successfully defend his title. The No 2 seed dropped a set for a second successive match as he navigated his way past the big serving Croatian Ivo Karlovic, winning 6-4, 4-6, 6-4, 6-4 in their fourth-round tie, despite his opponent firing down 28 aces. Nadal showed occasional flashes of his brilliant best as he overcame losing the second set to Karlovic to come through the encounter, but with the fifth seed Andy Murray awaiting him in the quarter-final tomorrow, he knows he has to raise his game. "The important thing: I am in the quarter-finals, losing only two sets," he said. "I think I am OK. I have to play better in the next match if I really want to have a chance to win. That's what I'm going to try. He [Murray] is one of the more difficult players to play against. I have to play my best tennis. "He's one of the most talented players on tour. He can play offensive, he can play defensive. He can do a lot of things during the same match. That's the most important thing." A lone break in the ninth game of the first set was enough to give Nadal the opening set, but he was unable to impose his game on his unseeded rival due to the sheer ferocity of the serves coming from Karlovic's racket. A scrappy game from Nadal in the 10th game of the second set ended with a shot from the baseline going long to hand Karlovic a break and the set to level things up. But if the blow of losing the set bothered Nadal, he did not let it show as he hit back, breaking in the third game of the next set, which was enough to go 2-1 up. A double fault in the third game of the fourth set handed Nadal another break and the Spaniard's powerful ground strokes saw him past the winning post, and he acknowledged that the high number of unreturnable serves from Karlovic had made it difficult for him to find his best form. "Today, the match is probably one of the most difficult matches to play well because it is without rhythm all the time," he said. "So the victory is the only thing in this kind of match. I think I returned aggressive. When I had a chance to touch the ball, I did well." A disappointed Karlovic said: "I had chances which I didn't take, and that's it." Murray's path to the last eight was far more comfortable as he proved too classy for John Isner in their match. Isner, the tallest player on the ATP Tour at 6ft 9ins, had a set point in the first set which he failed to take. Murray subsequently won the tiebreak and then never looked back as he cruised through the next two sets to triumph 7-6 (7-4), 6-3, 6-2. The Briton made only eight unforced errors in the entire match and said afterwards he was delighted with his display. "I thought it was a really good performance," he said. "I had, out of those unforced errors, probably three of them were in the 6‑5 game in the first set, and a couple early in one of my service games in maybe the second set. "So it was really good. I focused well, concentrated hard, and served well. Everything was good." Murray has yet to lose a set in this year's championship and said he believes he is improving with age. "Sometimes in the past, when I was sort of 18, 19, you know, I might have been getting worked up or not thinking about what I should be doing on the next point and worrying about what happened in the past. Now, it's just focus on each point. So you make the right decision more often. I guess it's a maturity thing. You learn to deal with the tight situations better and your focus holds for longer." The last time Murray played Nadal in a grand slam was at the US Open in 2008. The Briton won that match, and he is confident that he can again give his Spanish rival a headache or two when they face each other for a spot in the semi-finals at Melbourne Park. "Each time obviously it's a bit different [playing Nadal] and I have played some really good matches on hard courts with him," he said. "I think I've got some tactics that work well against him." * With agencies Coverage of the day's play on Abu Dhabi Sports 2 from 4pm
