Andy Murray celebrates winning the second set. Photograph: Paul Miller/EPA

Andy Murray's near-flawless progress in the Australian Open continued when he reduced the 6ft 9in American John Isner to a drained and dispirited wreck in straight sets to reach the quarter-finals in the best shape of all the remaining contenders. Murray will now play Rafael Nadal in the last eight after the Spaniard's win over Ivo Karlovic.

He is the only favoured seed to have not dropped a set, and beat Isner in style, 7-6, 6-3, 7-2 in 131 minutes of superb tennis.

Murray's serve – curiously questioned by some earlier in the week – was in a perfect groove, tactically he put Isner through the wringer, he hit several absolutely exquisite winners – and made only eight unforced errors.

He could hardly have done more. They had never met before and Isner, at least, will not look forward to an early rematch.

"I think he's got the best serve in the game," Murray said. "I had my coach serving at me from the service line but, once you get out there, it's still so tricky. I think he was a little bit tired. He'd won the tournament in Auckland last week and he's in the doubles.

"It's been good. I've moved really well since the start of the tournament and I hit some great shots on the run today."

He certainly did.

This was a match made in tennis heaven, given the perfectly meshed and contrasting styles of the combatants. Isner charged in on stilt-like legs behind his booming serve, Murray, one of the best returners in the game, looked to pass or lob the American.

Isner, who went out in the first round here twice before, had promised he'd come to the net – and that is where he went so regularly that Murray had no trouble finding open space.

He got the better of their fascinating duel in the first set. Isner was break point down at 2-2 and aced his way out of trouble, but Murray already looked to have his measure tactically. Isner blew the only break point he had in the set, and Murray won the tie-break.

In the second set Murray broke a flagging Isner, who sought refuge in the shade time and again as he found lugging his 17st 7lb frame through the noon-day sun debilitating.

The third set was not exactly a stroll for Murray, but he won in a canter at the end as Isner, dispirited and doomed, could do nothing against some of Murray's quite extraordinary ground strokes. One that will live in the memory came when the Scot was forced wide and deep behind the baseline, jumped like a dog through a hoop and double-fisted a backhand to the American's weary feet, which is where the ball stayed. Remarkable. He finished the break with an equally shattering backhand down the line, that left Isner bewildered.

Murray has his eyes firmly on the prize now.