MELBOURNE: Defending champion Novak Djokovic outlasted David Ferrer Wednesday to set up a repeat of last year’s Australian Open final with Andy Murray and ensure the “Big Four” all reached the semis.

The world No. 1 was worked hard by the fifth-seeded Spaniard, with the first two sets taking well over 2 hours but the Serb produced the goods when it mattered, stepping up his game to seal a 6-4, 7-6 (7/4), 6-1 victory.

In Friday’s semifinal he will face Murray, who enjoyed a smooth passage through to the last four, easing past rising Japanese star Kei Nishikori, 6-3, 6-3, 6-1 on a sun-baked Rod Laver Arena.

Roger Federer and Rafael Nadal will clash Thursday in the other half of the draw as the top four continue to exert an iron grip on the sport’s major titles.

Djokovic, pushed to four sets by Australian veteran Lleyton Hewitt in the fourth round, quickly found himself enmeshed in another physically draining battle as tenacious Ferrer hunted down every ball.

The Serb earned a crucial service break in the fifth game but had to wait nearly an hour to seal a first set full of punishing rallies.

Looking tired, Djokovic produced a stunning blind, backhand winner at full stretch from the back of the court early in the second, breaking in the first game.

The Serb suddenly looked in trouble when he grimaced in pain and clutched his left hamstring as Ferrer leveled at 2-2, but he did not appear to be restricted, going on to take the tiebreak and seize a two-set lead.

Djokovic shook off his discomfort and became more aggressive in the third set, breaking twice as Ferrer struggled to live with the greater intensity.

“Already after a couple of games I was feeling it was going to be a long match,” Djokovic said.

“There was a big mental advantage to getting two sets up,” he said, adding that he had stepped up his aggression as the match wore on.

Djokovic will face a confident Murray who says he is producing his best tennis on the game’s biggest stages after reaching his fifth consecutive Grand Slam semifinal.

In an entertaining match lasting 2 hours and 12 minutes, Nishikori wowed the crowd with a between-the-legs trick shot but could not produce the tennis to seriously trouble the British No. 1.

The Scot, 24, said he was delighted to be performing at the majors as he seeks his first Grand Slam title, after finishing runner-up in Melbourne in 2010 and 2011, and at the 2008 U.S. Open.

“It’s a difficult thing to do. It’s good to see that I’ve been playing my best tennis at the Slams because that’s something the last couple years I wanted to make sure I was doing,” said Murray. “That wasn’t always the case. Good to see that’s been paying off. I’ve been preparing the best I could for them.”

And Murray said he felt a relatively untroubled path to the semifinals that had rather left him fresh for tougher challenges ahead.

Murray called his fourth-round match against Mikhail Kukushkin “boring” after the Kazakh retired early in the third set. He also had an easy third-round win over Michael Llodra of France.

But Murray, who said he would relish another crack at Djokovic, said there was still room for improvement after a poor serving display in which he was on target with only 44 percent of his first serves.

The Scot, unbeaten this year after he won the Brisbane International, broke the Japanese 24th seed seven times in total while he was broken twice.

Nishikori was the first man from his country to reach the quarterfinals of the Australian Open.