ANDY Murray described as ‘‘boring’’ his 49-minute stroll against Mikhail Kukushkin at the Australian Open, but admitted it was good to get through to the quarter-finals with the minimum of effort.

Kukushkin was struggling from the outset with a left hip flexor problem, an injury sustained during his epic five-set win over Gael Monfils in the previous round, and was unable to put up a fight in what quickly became a lifeless encounter.

The unassuming Kazakh dragged it out for just over two sets but sensibly opted to retire when trailing 6-1 6-1 1-0 and with no chance of turning it around.

It was far from ideal and Murray, who will play Kei Nishikori next following the Japanese player’s victory over sixth seed Jo-Wilfried Tsonga, admitted he too had taken little enjoyment from it.

‘‘It was boring,’’ he said.

‘‘There was nothing happening on the court. I didn’t have to do anything, just hit the ball in court and he wasn’t running.

‘‘He was making mistakes the first or second ball of the rally. That was it.’’ The fourth seed felt Kukushkin had made the right decision to pull out when he did.

‘‘Yeah, because it was pointless, he wasn’t running,’’ he added. ‘‘The people probably weren’t enjoying the match, I certainly wasn’t.

‘‘There wasn’t any good points because he couldn’t move properly. Sometimes it’s just best to stop. I get to conserve a bit of energy but he was obviously struggling.’’ Murray had no idea coming into the match that the world number 92 was carrying a problem.

‘‘We practised on the court next to each other this morning, we both practised for about 40 minutes,’’ he said.

‘‘I saw him bouncing around before he went on court and it wasn’t until I went up 3-0 pretty quickly I realised he wasn’t really moving.’’ Lleyton Hewitt rolled back the years to deliver a typically gutsy display but it was not enough to derail Novak Djokovic’s title defence.

Hewitt looked down and out at two sets and 3-0 down but he stormed back to take the contest to a fourth set in which the world number one showed battling qualities of his own to edge through 6-1 6- 3 4-6 6-3 in nearly three hours.

For so long, it was one-way traffic with Hewitt looking flat and tired after his exertions against Andy Roddick and Milos Raonic in the previous rounds.

And Djokovic took full advantage, three breaks handing him the first set and three more moving him two sets up.

And when he won the first three games of the third, it seemed just a matter of time before victory was secured.

But, from nowhere, Hewitt found some form and, all of a sudden, Djokovic looked rattled.

The 30-year-old from Adelaide, twice a grand slam champion, dragged it back to 3-3, broke again for a 5-4 lead and then served it out.

And when Djokovic faced another break point in the third game of the fourth set, the comeback looked set to continue. But the Serbian held his nerve to win the game and with that he regained the momentum.

He claimed the Hewitt serve to go 4-2 up and it proved a lead he would not relinquish.

‘‘I have to give credit to my opponent who never gives up,’’ said Djokovic.

‘‘He’s a great competitor and he kept on making me play an extra shot. I made a couple of unforced errors and he got back into the match. I have a lot of respect for him.

‘‘For two sets and 3-0 I was playing really well and then I stopped moving but credit to him, he wasn’t making any unforced errors.’’ Next for Djokovic is a meeting with fifth seed David Ferrer in the last eight.

The Spaniard was an impressive winner, beating Richard Gasquet 6-4 6-4 6-1.