• Australian Open, Day Five

Unconvincing Nadal sets up Karlovic clash

Rafael Nadal whips a forehand past the gutsy Philipp Kohlschreiber © Getty Images

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Third round in pictures

Rafael Nadal was far from his domineering self as he battled his way into the Australian Open fourth round, beating Philipp Kohlschreiber in four sets.

The former world No.1 is still fighting for his best form following knee problems suffered in 2009, and he needed all his trademark determination to triumph 6-4 6-4 2-6 7-5. Nadal will know he needs to up his game if he is to claim his seventh Grand Slam title though, after Kohlschreiber's solid defensive game highlighted a worrying lack of power from the Spaniard.

Having moved to a two-set lead in fairly routine fashion, Nadal allowed Kohlschreiber to grow into the contest at the start of the third, the German breaking twice to cut the deficit and then threatening to overhaul his opponent's serve again in the pivotal second game of the fourth set. Attacking Nadal's serve, Kohlschreiber racked up a plethora of break points as the scores stayed locked at deuce for 15 minutes, but it was the reigning champion who clung on to hold serve.

From there Nadal built momentum, finding a break of his own to close out the match and set up a fourth-round tie with Ivo Karlovic, who smashed 33 aces to overcome Ivan Ljubicic 6-3 3-6 6-3 7-6(7).

Crowd favourite Andy Roddick was made to work hard to see off Feliciano Lopez 6-7(4) 6-4 6-4 7-6(3) in the battle of the big serves in round three. Both players struggled to break each other and Roddick will not have enjoyed spending over three hours in the afternoon heat in what he might have hoped would be a more routine examination.

Lopez irritated the sometimes fiery American throughout Friday's contest, questioning both the umpire and his opponent on one particular occasion before deciding whether or not to make a challenge. The Spaniard was also able to match Roddick's 29 aces, but was ultimately let down by 60 unforced errors.

Former world No.1 Roddick took all the momentum into the contest, riding a seven-match winning streak that brought him the title in Brisbane. The American had also never lost to Lopez, yet that looked a distinct possibility when the Spaniard snatched the first-set tie-breaker 7-4.

As serves dominated, it became obvious that any break would win the set and it was Roddick who had the necessary variety in his game. A crucial triumph against the serve in game five of the second set restored parity, before another in game nine of the third put him in the driving seat.

A second tie-breaker went the way of the 2003 US Open champion as he closed out the match, and Roddick admitted in the aftermath: "I'm relieved to get through to the next round."

Next up for the big-serving American is a tussle with Fernando Gonzalez, who showed typical grit to fight through a five-setter to beat Kazakhstan's Evgeny Korolev 6-7(5) 6-3 1-6 6-3 6-4.

Andy Murray will face the challenge of 6ft 9in giant John Isner in round four after the American produced a surprise victory over 12th seed Gael Monfils. Seeded 21 places lower than his French counterpart, Isner simply blew Monfils off the court with a 6-1 4-6 7-6(4) 7-6(5) victory.

Posing such a towering threat, Isner's serve inevitably proved a vital factor in keeping Monfils at arm's length, winning two tie-breakers to clinch the contest. Only in the second set did Monfils ever suggest he may be coming to terms with his opponent's power, but that challenge now rests with Murray as Isner advances in ominous fashion.

Juan Del Potro gets the crowd involved during his victory over Florian Mayer © Getty Images

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Juan Martin Del Potro appears determined to do things the hard way, following up his five-set epic against James Blake with another hard-fought victory over Florian Mayer in round three. The 2009 US Open champion completely lost his way at the beginning of the second set against Mayer, losing the set to love before regaining his composure to advance 6-3 0-6 6-4 7-5.

The extended match time will nevertheless be a concern to Del Potro, who has already played 13 sets of tennis in the tournament and has been prone to some notorious collapses in fitness in the past. The Argentinean is scheduled for a potential meeting with Murray in the semi-finals.

First Del Potro must overcome 14th seed Marin Cilic, who recovered from a one-set deficit to beat the dangerous Stanislas Wawrinka. Despite finishing his second round match at 2am on Thursday, Cilic blew away the early cobwebs to triumph 4-6 6-4 6-3 6-3 and set up a rematch of Del Potro's 2009 US Open quarter final win over the Croat.

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