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Andy Murray produced a magnificent all-round performance to outclass John Isner and reach the Australian Open quarter-finals for the first time.

Britain's Murray made only eight unforced errors in beating his 6ft 9ins American opponent 7-6 (7-4) 6-3 6-2.

The Scot saved a set point in the opener but ruthlessly exposed a tiring Isner thereafter and had the crowd on its feet as he sealed a fine victory.

Fifth seed Murray next plays Rafael Nadal after he overcame Ivo Karlovic.

But the defending champion will not relish the prospect of facing Murray, who is still yet to drop a set all tournament.

"I served really smart, hits some great shots and stayed tough," he told BBC Sport after disposing of Isner in two hours and 12 minutes.

"You need to make sure you put a lot of first serves in and try not to let him dictate. I just tried to get his serves back.

"It's been a great start and I was always going to have to play my best tennis. Now the matches are going to get tougher."

Murray, who lost to Fernando Verdasco at this stage in 2009, came into the match well aware of the danger posed by his giant opponent.

Isner collected his maiden ATP Tour title at the recent Auckland Open and served 81 aces en route to round four at Melbourne Park.

And the American immediately signalled his intent with a commanding hold to love in game one, displaying all the attributes that have aided his rise to a career-high ranking of 28.

But Murray looked comfortable with the task at hand and more than matched Isner in the early exchanges, serving magnificently, moving gracefully and dominating rallies.

The Scot conceded only two points in his opening five service games and was recording a first serve percentage of about 80%.

With his own house very much in order, Murray began to attack the Isner serve with increased aggression and forced the American to pull a backhand wide to bring up a break point in game five.

Isner serve-volleyed his way out of trouble and there was little to choose between the players until Murray netted a forehand in game 12 to hand over a set point, but he too held and forced a tie-break.

Both men played with freedom but it was Murray who got the mini-break at 4-3 after Isner sent down an untimely double fault.

Murray took the set when Isner netted a drop shot, bounding to his seat as the crowd on Rod Laver Arena acclaimed a near-faultless set from the world number five.

Although Isner kept the scoreboard ticking over at the beginning of the second set, the 24-year-old from North Carolina appeared to be flagging in the Melbourne heat.

He went to five sets by Andreas Seppi in round one, struggled an arm problem against Louk Sorensen in the second round and was now being given the run-around by one of the ATP Tour's fittest players.

Isner scrambled to save break points in games four and six but there was no way out in game eight when Murray broke to love with a rasping forehand winner for a 5-3 lead.

There were nervy glances between Murray and his support team in the stands as he faced two break-back points when serving for the set, but a resounding drive volley and a cute cross-court backhand averted the danger.

An animated Murray then let out a huge roar as Isner lashed a forehand into the tramlines to hand over the set.

Isner's physical condition continued to deteriorate in the final set and Murray, sensing his chance to wrap up the match, simply piled on the pressure.

The 6ft 3ins from Dunblane was reeling off one winner after the next and he brought up three breaks points in game five by racing across the baseline to retrieve a smash and delivering a stunning backhand that Isner could only net.

Murray broke at the first time of asking with a jaw-dropping running backhand pass down the line and soon made it 5-2 as Isner's game fell apart.

Isner's frustration was clear - he received a warning from chair umpire Carlos Ramos for smashing a racquet - and his campaign was ended when Murray converted the first of two set points with a delicious forehand drop shot.